Folate deficiency among women of reproductive age in Ethiopia: A systematic review and meta-analysis

Berhe Gebremichael; Hirbo Shore Roba; Alemeshet Getachew; Dejene Tesfaye; Haftu Asmerom

doi:10.1371/journal.pone.0285281

. 2023 May 8;18(5):e0285281. doi: 10.1371/journal.pone.0285281

Folate deficiency among women of reproductive age in Ethiopia: A systematic review and meta-analysis

Berhe Gebremichael ^1,^*, Hirbo Shore Roba ^1,², Alemeshet Getachew ¹, Dejene Tesfaye ³, Haftu Asmerom ⁴

Editor: Abdu Oumer⁵

PMCID: PMC10166565 PMID: 37155667

Abstract

Background

Folate deficiency (FD) can cause adverse health outcomes of public health significance. Although FD is a significant micronutrient deficiency in Ethiopia, concrete evidence is limited. Therefore, this systematic review and meta-analysis was designed to estimate the pooled prevalence of FD among women of reproductive age (WRA).

Methods

A systematic literature search was performed using MEDLINE, Embase, CINAHL, Google Scholar, African Journals Online (AJOL), The Vitamin and Mineral Nutrition Information System (VMNIS) of the World Health Organization (WHO), Global Health Data Exchange (GHDx), and institutional repositories of major universities and research centers. Additionally, we scanned the reference lists of relevant articles. Two authors independently selected the studies, extracted the data, and the study risk of bias. Heterogeneity was assessed using the I² statistic. We used a random-effects model to estimate the pooled mean serum/plasma folate and the pooled prevalence of FD. Begg’s and Egger’s tests were used to check publication bias.

Results

Ten studies—nine cross-sectional and one case-control—with a total of 5,623 WRA were included in the systematic review and meta-analysis. Four (WRA = 1,619) and eight (WRA = 5,196) cross-sectional studies were used to estimate the pooled mean serum/plasma folate and prevalence of FD, respectively. The pooled mean serum/plasma folate concentration estimate was 7.14 ng/ml (95% CI: 5.73, 8.54), and the pooled prevalence of FD was estimated to be 20.80% (95% CI: 11.29, 32.27). In addition the meta-regression analysis showed that the sampling technique was significantly associated with mean serum/plasma folate concentration.

Conclusions

FD is a significant public health issue among WRA in Ethiopia. Therefore, the public health strategies of the country should focus on promoting the consumption of folate-rich foods, strengthening the coverage of folic acid supplementation and its adherence, and swift translation of the mandatory folic acid fortification into action.

Systematic review registration

PROSPERO 2022—CRD42022306266.

Introduction

Folate is a naturally occurring essential vitamin mainly found in green leafy vegetables and legumes [1]. It is necessary for deoxyribonucleic acid (DNA) replication and normal cell formation and growth [2]. Therefore, folate deficiency (FD) reduces thymidylic acid and increases homocysteine in the body, resulting in several health risks [3].

Folate deficiency is caused primarily by inadequate dietary intake [4, 5] and partly by medical and physiologic conditions that increase the need or excretion of folate [5–8]. Different study findings show that iron deficiency anemia [4, 9], knowledge of folate-rich foods [4, 10], and folic acid supplementation [11] are significantly associated with FD. Folate intake is suboptimal in the diets of many WRA and exacerbated by overcooking foods and poor bioavailability [8], estimated to be from 50% to 82% [12, 13]. In several developed countries, fortifying grains with folic acid has increased folate intake [14]. However, in Ethiopia, the unavailability of fortified foods further increases the risk of folate insufficiency, particularly for vulnerable populations such as WRA [4, 15].

A definition for what constitutes a public health problem for folate deficiency is not well established [16] due to limited relevant population-based data [17]. However, a 5% and above prevalence generally represents a public health problem [16–19]. Therefore, folate deficiency is considered a severe public health issue, especially among disadvantaged groups in developing countries, including Ethiopia [20, 21]; some of the most affected groups by FD include WRA [5, 7, 17].

According to a global systematic review based on the available evidence of folate status in WRA, the prevalence of FD was greater than 20% in many low-income countries, which is far above the general threshold for public health concerns. However, in high-income countries, the prevalence was less than 5%. In this review the prevalence of folate insufficiency was more than 40% in most countries [22]. Among different African countries, the prevalence of FD in pregnant women fluctuated from 0.8% in Kenya to 86.1% in Côte d’Ivoire [9, 23–26]. Similarly, different study findings in Ethiopia show the prevalence of FD in WRA ranging from 1.9% to 46% [4, 10, 27–32]. However, in most of these studies, the prevalence of FD was above 5%—indicating its public health significance in the country.

The consequences of FD among WRA include megaloblastic anemia [8, 33–35] and neural tube defects (NTDs) [36–39]. Maternal anemia is highly prevalent in Ethiopia [40]; however, reports showing FD as the etiology of anemia are unavailable. Folate deficiency is a significant risk factor for neural tube defects (NTDs), which affects more than 300,000 births worldwide and 65 per 10,000 births in Ethiopia [36–39]. As countries progress in reducing child mortality from infectious diseases, congenital disabilities become a more significant cause of under‐five mortality in many countries [41]. Other consequences of FD include abortion [33–35], preterm birth [33], and hyperhomocysteinemia, which is a risk factor for metabolic and cardiovascular diseases [3, 34, 35, 42].

Folate deficiency among WRA is one of the significant public health issues in Ethiopia [43]. Therefore, to address this problem, the Ethiopian Government adopted the global targeted iron and folic acid supplementation for pregnant women during their antenatal care visits to reduce the prevalence of anemia in WRA and children under five [44]. Additionally, in 2022, the country endorsed the mandatory fortification of edible oil and wheat flour with folic acid, an effective intervention strategy to overcome the burden of FD [45]. However, to our knowledge, no systematic review and meta-analysis study has addressed FD among WRA in Ethiopia to provide high-level evidence for policymakers to track the progress, evaluate the impact of existing programs and design further context-specific interventions. Therefore, this systematic review and meta-analysis was designed to address the gap and estimate the exact prevalence of FD among WRA in Ethiopia.

Methods and materials

Registration

This systematic review and meta-analysis was performed, according to the protocol registered in the International Prospective Register of Systematic Reviews (PROSPERO) on 22 February 2022, with registration ID: CRD42022306266.

Search strategy

Studies were identified by searching electronic databases, institutional and organizational repositories, and websites. Additionally, the reference lists of key articles were examined to retrieve additional related studies. From the electronic databases, we searched MEDLINE (via PubMed), Embase (via Ovid), CINAHL (via EBSCOhost), African Journals Online (AJOL), and Google Scholar. The Vitamin and Mineral Nutrition Information System (VMNIS) of the World Health Organization (WHO), Global Health Data Exchange (GHDx), institutional repositories of major universities (including Addis Ababa University, Jimma University, Hawassa University, Haramaya University, Arbaminch University, University of Gondar, Bahir Dar University, and Mekelle University), and the institutional repositories of research centers (including the Ethiopian Public Health Institute (EPHI), Ethiopian Health and Nutrition Research Institute (EHNRI) and Ethiopian Nutrition Institute (ENI)) were searched for reports and unpublished articles.

The search was first conducted on 28 February 2022, and updated on 31 May 2022. Two authors (BG and HSR) performed the search activities independently. The following search terms were used to find all relevant studies in the databases and other sources: "prevalence", "magnitude", "status", "level", "folate", "folic acid", "micronutrient", "deficiency" and "Ethiopia". The search terms were used separately and in combination using the Boolean operators ’OR’ and ’AND’ (S1 Text). The PRISMA guideline for systematic review [46] was used to report the search results.

Eligibility criteria

The studies which fulfilled the following criteria were included: all observational study designs (cross-sectional, case-control, and cohort studies) which reported mean or median serum or plasma folate, or prevalence of FD, published in the English language from 2004 to 2022, full-text articles, conducted among WRA (15–49 years old) in Ethiopia, studies with a response rate greater than 80%, reporting quality assurance methods, and quality assessment score better than 50%. For any studies from the same survey, we selected and included the study that reported the desired outcomes and the extracted variables clearly. Studies were excluded if they were found to have a poor quality score as per the stated criteria, were review articles, qualitative studies, abstracts, or failed to determine the desired outcomes (i.e., mean or median serum or plasma folate or FD).

The outcome variable was ’folate deficiency’ and was defined according to the WHO recommendation as follows: (1) serum or plasma folate <3 ng/mL or red blood cells (RBC) folate <100 ng/mL (using macrocytic anaemia as a haematological indicator); (2) serum or plasma folate <4 ng/mL or RBC folate <151 ng/mL (using homocysteine concentration as a metabolic indicator). Folate insufficiency (level of folate below which is a risk for NTD) was defined as RBC folate < 400 ng/mL [47].

Study risk of bias and quality assessment

We assessed the risk of bias and quality of the included studies using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Studies Reporting Prevalence Data [48]. The checklist contains nine items: (1) appropriateness of the sample frame to address the target population, (2) appropriateness of sampling procedure/technique, (3) adequacy of sample size, (4) detail description of study subjects and setting, (5) sufficiency of data analysis coverage of the identified sample, (6) validity of methods used for the identification of the condition, (7) measurement of the condition in a standard and reliable way for all WRA, (8) appropriateness of statistical analysis, and (9) adequacy of response rate and appropriateness of management of low response rate.

Two review authors (BG and HSR) independently applied the checklist to assess the risk of bias in each included study. If there were any discrepancies between the two review authors, first, the two authors discussed the issue trying to reach a consensus, with a third review author (AG, DT or HA) acting as an arbiter if necessary. Finally, studies with a quality assessment score of greater than 50% were included in the systematic review; fortunately, all the assessed studies scored above 60% (S1 Table).

Data collection (extraction) process

A structured data extraction format, prepared using Microsoft Excel 2010, was used to extract all the necessary data. Two reviewers (BG and HSR) independently extracted the data from the eligible studies. Disagreements between the two authors were resolved through discussions and consultations with a third review author (AG, DT or HA). For each included study, we extracted the following study characteristics: authors’ names and publication date, study year, study setting, study scale/level, study population, sample size, sampling technique, response rate, mean age of WRA, fasting status of WRA during blood sample taking, laboratory assay methods and biomarkers used, cut-off-point used, mean or median serum and/or RBC folate concentration, the prevalence of FD and associated factors of FD.

Data synthesis and analysis

The meta-analyses were performed using STATA version 16.0 statistical software package. A random-effects model was applied to estimate the pooled mean serum/plasma folate level and the pooled prevalence of FD in WRA [49]. We used the metan and metaprop STATA commands to estimate the pooled mean serum or plasma folate and the pooled prevalence of FD, respectively. The standard error for mean serum/plasma folate was generated using the following formula: $se = \frac{SD}{\sqrt{n}}$ [50], where se = standard error, SD = Standard Deviation and n = sample size. We generated and used the standard error instead of standard deviation to give more weight to studies with precise estimates and to include the role of sample size in the estimation.

Forest plots were used to present the results of pooled estimates with a 95% confidence interval (CI). The I² statistic was used to test heterogeneity among studies. To explore the sources of heterogeniety, subgroup analysis was done for the mean serum/plasma folate level by survey year and sampling technique. Additionally, subgroup analysis was done for the prevalence of FD by population group and mean age of WRA. Begg’s rank correlation test and Egger’s linear regression test were used to check for the publication bias. Leave-one-out sensitivity analysis was performed to show how each individual study affects the overall estimate of the rest of the studie. Finally, meta-regression analyses were carried out to identify parameters associated with FD.

Ethics statement

All analyses were based on previously done original studies. Therefore, no ethics approval or patient/participant consent was required.

Results

Study selection process

Initially, 1600 studies were identified from the electronic searches. Of these, 1560 were published articles, while 40 were theses and organizational reports. After removing 97 duplicates, 1503 records were screened by title and abstract, and 1467 studies were excluded. Next, 36 records were further assessed for risk of bias and eligibility, and 26 studies were excluded (23 did not meet the eligibility criteria, and three had duplicated content). Finally, ten studies were included in the systematic review and meta-analysis (Fig 1).

Characteristics of included studies

This systematic review and meta-analysis included 10 studies [4, 10, 27–32, 51, 52] with a total of 5,623 WRA, which were conducted between 2004 and 2022. Among the studies, nine [4, 10, 27–32, 52] were cross-sectional studies, and one was a case-control [51]. Regarding the study setting, six of the studies [4, 27, 28, 30, 31, 52] were done at the community level, while the other four [10, 29, 32, 51] were institutional-based. Three studies [4, 28, 30] were conducted at a national level, whereas the other seven were conducted at the sub-national/local level—three in Oromia Region [29, 32, 52], one in Amhara Region [31], one in Sidama Region [27], and two in Addis Ababa City Administration [10, 51].

Six studies [10, 27, 29, 32, 51, 52] were conducted among pregnant women, and two were [28, 30] done among non-pregnant/non-lactating women. However, two studies [4, 31] were performed generally in WRA without specifying the physiological status of the women. Five studies [4, 28, 30, 31, 52] applied probability sampling techniques, while the other five [10, 27, 29, 32, 51] used non-probability sampling. The sample size of the studies ranged from 99 [27] to 1647 [30], with response rates ranging from 89.5% [31] to 100% [4, 28, 29, 32, 51]. Nine of the studies [4, 10, 27, 29–32, 51, 52] reported mean (+ SD) age of the WRA, ranging from 24.5 (+ 5.0) [32] to 33.1 (+ 7.2) [31] years.

Concerning the laboratory methods, three studies [4, 10, 51] used fasting blood samples, one [27] used non-fasting blood samples, and six studies [28–32, 52] did not report the fasting status. Seven studies [4, 10, 27, 29, 32, 51, 52] used one of the protein binding assays to assess folate status, two studies [30, 31] used microbiological assays, and one study [28] did not report the type of assay used. Additionally, eight studies [4, 27–29, 31, 32, 51, 52] reported serum/plasma folate as a biomarker, one reported RBC folate [10], and one study reported both serum and RBC folate [30].

Out of those included, six of the cross-sectional studies [4, 27, 29, 31, 52] reported mean (+ SD) serum/plasma folate concentration, ranging from 4.5 ng/ml (+ 0.1) in Oromia Region [52] to 12.6 ng/ml (SD not reported) in Amhara Region [31]. The single case-control study [51] also reported mean (+ SD) serum/plasma folate concentration for the cases (4.4 ng/ml (+ 1.8)), and controls (8.0 ng/ml (+ 3.0)), separately. On the other hand, one cross-sectional study [32] reported median (IQR) serum folate concentration as 4.2 ng/ml (2.3) and the case-control study [51] reported 4.8 ng/ml (3.7) for the cases and 8.9 ng/ml (5.3) for the controls. Whereas, one study [10] reported median (IQR) RBC folate concentration as 585 ng/ml (IQR not reported), and another one study [30] reported both median (IQR) serum and RBC folate concentrations as 5.0 ng/ml (4.5) and 255.5 ng/ml (174), respectively.

Eight of the cross-sectional studies [4, 27–32, 52] reported FD fluctuating from 1.9% [31] in Amhara Region to 46.0% [4] in a national study. Three of these studies [4, 29, 31] also reported possible or marginal FD, varying from 2.6% [31] to 21.2% [4]. On the other hand, the case-control study [51] merged the FD and possible FD, and found 57% for the cases and 33.5% for the controls. However, one cross-sectional study [10] reported folate insufficiency instead of FD.

From all studies, two [4, 52] described four factors associated with FD, while another study [10] found one associated with folate insufficiency. Accordingly, poor vegetable and grain intake [4], poor knowledge on folate-rich foods [52], iron deficiency anemia [4, 52], and no iron-folic acid supplementation [52] were identified as the significant predictors of FD. Similarly, poor vegetable intake [10] was significantly associated with folate insufficiency (Table 1).

Table 1. Summary characteristics of the 10 studies included in the systematic review and meta-analysis of folate deficiency among women of reproductive age in Ethiopia, 2022.

Study	Study year	Study area	Population	Sampling	Study setting	Fasting status	Lab assay method	Bio-marker	Cutt-off (in ng/ml)	Sample size	Response rate	Mean age (+SD) in yeas	Mean folate (+SD) in ng/ml	Median folate (IQR) in ng/ml	Marginal FD (%)	FD (%)	Factors associated with FD
Adela et al., 2018	2017	Addis Ababa	Pregnant women	Non-probability	Institution	Fasting	PBA (ECLIA; Roche Elecsys^®)	RBC	<400	160	98.8	26.5 (4)	NR	585 (NR)	NR	27.5^*	Reported^a
Bekele and Baye, 2019	2018	Amhara	WRA	Probability	Community	NR	MBA (5-methyl-THF calibrator)	Serum	<6.6; <4	179	89.5	33.1 (7.2)	12.6 (NR)	NR	2.6	1.9	NR
Bromage et al, 2021	2019	National	Non-pregnant/non-lactating	Probability	Community	NR	NR	Serum	<3	1604	100	NR	NR	NR	NR	31.8	NR
Elema et al., 2018	2015	Oromia	Pregnant women	Non-probability	Institution	NR	PBA (ECLIA; Roche Elecsys^®)	Serum	<3	104	100	24.6 (5)	7.6 (3.5)	NR	10.6	17.3	NR
EPHI, 2016	2015	National	Non-pregnant	Probability	Community	NR	MBA (calibrator NR)	RBC	<151	1647	94.5	28.9 (8.8)	NR	255.5 (174)	NR	32.0	NR
EPHI, 2016	2015	National	Non-pregnant	Probability	Community	NR	MBA (calibrator NR)	Serum	<4	1647	94.5	28.9 (8.8)	NR	5.0 (4.5)	NR	17.3	NR
Gibson et al., 2008	2004	Sidama	Pregnant women	Non-probability	Community	Non-fasting	PBA (RIA; DPC Dual CountTM Solid Phase No Boil)	Plasma	<3	99	94.9	27.8 (4.6)	11.5 (5.6)	NR	NR	2.1	NR
Haidar et al., 2010	2005	National	WRA	Probability	Community	Fasting	PBA (ELISA; Roche Elecsys^®)	Plasma	<6.6; <4	970	100	32.6 (12.5)	5.6 (3.8)	NR	21.2	46	Reported^b
Kucha et al., 2022^**	2020	Addis Ababa	Pregnant women	Non-probability	Institution	Fasting	PBA (ELISA; Cloud-Clone Corp. Katy, TX, USA)	Serum	<6	Cases: 100	100	Cases: 26.8 (5.3)	Cases: 4.4 (1.8)	Cases: 4.8 (3.7)	Cases: 57		NR
Kucha et al., 2022^**	2020	Addis Ababa	Pregnant women	Non-probability	Institution	Fasting	PBA (ELISA; Cloud-Clone Corp. Katy, TX, USA)	Serum	<6	Controls: 167	100	Controls: 27.2 (4)	Controls: 8 (3)	Controls: 8.9 (5.3)	Controls: 33.5		NR
Mebratu and Baye, 2016	2015	Oromia	Pregnant women	Non-probability	Institution	NR	PBA (ECLIA; Roche cobas^® c501)	Serum	<3	147	100	24.5 (5)	NR	4.2 (2.3)	NR	21.8	NR
Yusuf et al., 2021	2021	Oromia	Pregnant women	Probability	Community	NR	PBA (ECLIA; Roche cobas^® e411)	Serum	<4	446	96.8	25.7 (5.2)	4.5 (0.1)	NR	NR	49.3	Reported^c

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SD: standard deviation

IQR: inter-quartile range

FD: folate deficiency

PBA: protein binding assay

ECLIA: electrochemiluminescence immunoassay

RBC: red blood cell

NR: not reported

WRA: women of reproductive age

MBA: microbiological assay

THF: tetrahydrofolate

EPHI: Ethiopia Public Health Institute

RIA: Radioimmunoassay

ELISA: enzyme-linked immunosorbent assay

^apoor vegetable intake was reported as associated factor

^bpoor vegetable and grain intake, and iron deficiency anemia were reported as associated factors

^cpoor knowledge on folate rich foods, iron deficiency anemia and iron-folic acid supplementation were reported as associated factors

*This study reported folate insufficiency, not folate deficiency

**This is the only case-control study, and it did not report the possible/marginal FD and FD separately; they were merged

Risk of bias and quality assessment

The risk of bias and quality of the studies was assessed by the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Studies Reporting Prevalence Data [48], a 9-item based checklist, indicated in the methods and materials section. The overall quality assessment score, with a potential total of 9 points, ranged from 6 (66.7%) to 9 (100%) points. In all (100%) of the included studies, the study subjects and settings were described in detail; valid methods were used for the identification of the condition; the data analysis was performed with sufficient coverage of the identified samples and response rates were adequate. However, the sampling of WRA was inappropriate in 5 (50%) of the studies and sample size was inadequate in 6 (60%) studies (S1 Table).

Mean serum/plasma folate concentration

Four cross-sectional studies totaling 1,619 WRA were included in the meta-analysis to estimate the pooled mean serum/plasma folate level. Three of the studies [4, 27, 29] were published articles, and one was a master thesis [52]. Two of the studies were from Oromia Region [29, 52], one was from Sidama Region [27], and one [4] was a national study. Concerning the study setting, three studies [4, 27, 52] were community-based whereas one [29] was an institution-based study. The studies were conducted in 2004 [27], 2005 [4], 2015 [29] and 2021 [52]. Three studies [27, 29, 52] were conducted in pregnant women, while one [4] was in WRA. All four studies used protein binding assay to analyze the serum/plasma folate level. Two studies [4, 52] used probability sampling and the other two [27, 29] used non-probability sampling. The sample size of the studies ranged from 99 [27] to 970 [4], with a response rate ranging from 94.5% [27] to 100% [4, 29]. The mean (+ SD) serum/plasma folate concentration varies from 4.5 ng/ml (+ 0.1) [52] to 11.5 ng/ml (+ 5.6) [27] (Table 1).

The meta-analysis revealed that the pooled estimate of the mean serum/plasma folate concentration was 7.14 ng/ml (95% CI: 5.73, 8.54). The analysis revealed considerable between-study heterogeneity (I² = 99.0%, p = 0.000) (Fig 2). The Egger’s test detected significant publication bias (p = 0.000), however, it was not detected in the Begg’s test (p = 0.09).

Fig 2 — NOTE: Weights are from random-effects model.

Prevalence of folate deficiency

The meta-analysis included eight cross-sectional studies conducted from 2004 to 2021, with a total of 5196 WRA, to estimate the pooled prevalence of FD. Four of the studies [4, 27–29] were published articles, three [31, 32, 52] were master theses, and one [30] was an organization survey report. Six of the studies [4, 27, 28, 30, 31, 52] were community-based and two [29, 32] were institutional-based. Of the eight studies, three [4, 28, 30] were done at national level, while five were conducted at the sub-national/local level—three studies were from Oromia Region [29, 32, 52], one from Amhara Region [31], and one from Sidama Region [27]. Pregnant women were the target group in four studies [27, 29, 32, 52], and non-pregnant/non-lactating women were the targets of two studies [28, 30]. Nevertheless, two studies [4, 31] were done generally in WRA without specifying the physiological status of the women. Five studies [4, 27, 29, 32, 52] used protein binding assays, two [30, 31] used microbiological assays, and one [28] did not report the type of laboratory assay. From the studies, five [4, 28, 30, 31, 52] applied probability sampling techniques, while three [27, 29, 32] used non-probability sampling. The sample varied from 99 [27] to 1647 [30], with response rates ranging from 89.5% [31] to 100% [4, 28, 29, 32]. The prevalence of FD was widespread from 1.9% [31] in a study reported from Amhara Region to 46.0% [4] in a national study (Table 1).

In this meta-analysis, the pooled prevalence of FD was estimated to be 20.80% (95% CI: 11.29, 32.27). The meta-analysis indicated marked evidence of heterogeneity among the studies (I² = 98.71%, p = 0.00) (Fig 3). No significant publication bias was detected using Egger’s (p = 0.51) and Begg’s (p = 0.17) tests.

Subgroup analysis for mean serum/plasma folate concentration

To explore sources of heterogeneity, sub-group analyses were performed for the mean serum/plasma folate level by survey year and sampling technique. Consequently, the level of mean serum/plasma folate was higher among studies from 2015 or earlier (n = 3), (8.18 ng/ml, 95% CI: 5.38, 10.98) compared to those conducted after 2015 (n = 1) (4.50 ng/ml, 95% CI: 4.49, 4.51). There was considerable between-group heterogeneity (p = 0.01) (Fig 4).

Fig 4 — NOTE: Weights and between-subgroup heterogeneity test are from random-effects model.

Likewise, the mean serum/plasma folate was higher among studies which used non-probability sampling techniques (n = 2) (9.52 ng/ml, 95% CI: 5.70, 13.34) compared to those that used probability sampling (n = 2) (5.04 ng/ml, 95% CI: 3.97, 6.12). Significant heterogeneity was observed between the groups (p = 0.03) (Fig 5).

Fig 5 — NOTE: Weights and between-subgroup heterogeneity test are from random-effects model.

Subgroup analysis for the prevalence of folate deficiency

We also performed subgroup analyses for the prevalence of FD to find out the possible sources of heterogeneity. Subgroup analysis by population/target group indicated that the prevalence of FD was higher among WRA (unspecified/general population group) (n = 2), (36.73%, 95% CI: 33.96, 39.55) than the non-pregnant/non-lactating (n = 2), (24.08%, 95% CI: 22.63, 25.57) and pregnant women (n = 4), (20.01, 95% CI: 3.34, 45.44). The between-groups heterogeneity was significant (p = 0.000) (Fig 6).

In the same way, the prevalence of FD was higher among women older than 30 years (n = 2), (36.73%, 95% CI: 33.96, 39.55) compared to those aged 30 years or less (n = 5), (19.53%, 95% CI: 7.10, 36.10). Significant between-groups heterogeneity was observed (p = 0.045) (Fig 7).

Sensitivity analysis

We performed influential sensitivity (leave-one-out) analysis to assess the effect of each individual study on the observed heterogeneity. Accordingly, the overall point estimate fell within the CI of each sub-set of the studies obtained by leaving out exactly one study. This indicates that no individual study significantly affected the overall estimate of the rest of the studies (Table 2).

Table 2. Leave-one-out sensitivity analysis showing the influence of each individual study on the overall estimate in the mean serum/plasma folate level (n = 4) and the prevalence of folate deficiency (n = 8) among women of reproductive age in Ethiopia, 2022.

Study omitted	Pooled mean serum/plasma folate level in ng/ml (95% CI)	Pooled prevalence of folate deficiency (95% CI)
Bekele and Baye, 2019	—	24.89 (14.93, 36.41)
Bromage et al, 2021	—	19.21 (7.67, 34.32)
EPHI, 2016	—	21.30 (10.58, 34.49)
Elema et al., 2018	6.94 (5.46, 8.43)	21.29 (11.03, 33.77)
Gibson et al., 2008	5.84 (4.65, 7.03)	24.49 (14.09, 36.66)
Haidar et al., 2010	7.83 (4.25, 11.41)	17.64 (8.61, 28.98)
Mebratu and Baye, 20	—	20.65 (10.44, 33.20)
Yusuf et al., 2021	8.18 (5.38, 10.98)	17.31 (8.30, 28.71)
Combined (overall)	7.14 (5.73, 8.54)	20.80 (11.29, 32.27)

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Meta-regression

Meta-regression was performed for the mean serum/plasma folate level and FD for covariates to explain the possible sources of heterogeneities observed in the studies. Accordingly, sampling technique was found to be the only covariate significantly associated with mean serum/plasma folate. The application of non-probability sampling technique increased the mean serum/plasma folate level by 4.45 ng/ml (95% CI: 0.57, 8.33; p = 0.025) compared to probability sampling method. No covariate showed a significant association with FD (Table 3).

Table 3. Meta-regression result of covariates to explain heterogeneity observed in the mean serum/plasma folate level (n = 4) and folate deficiency (n = 8) among women of reproductive age in Ethiopia, 2022.

Outcome variable	Covariates	Coefficient (95% CI)	Standard Error	P-value
	Survey year
	2015 or earlier	3.70 (-3.01, 10.41)	0.34	0.28
	After 2015	Reference
	Scale of study
	National	-2.23 (-10.12, 5.65)	4.02	0.58
	Sub-national/local	Reference
	Study setting
	Community-based	-0.43 (-8.90, 8.02)	4.31	0.92
	Institution-based	Reference
	Sampling technique
	Non-probability	4.45 (0.57, 8.33)	1.98	0.03
	Probability	Reference
	Sample size
	<500	2.23 (-5.65, 10.12)	4.02	0.58
	>500	Reference
	Mean age	-0.09 (-1.28, 1.10)	0.61	0.89
Folate deficiency	Survey year
	2015 or earlier	-0.07 (-0.34, 0.21)	0.14	0.64
	After 2015	Reference
	Scale of study
	National	0.12 (-0.14, 0.38)	0.13	0.34
	Sub-national/local	Reference
	Study setting
	Community-based	0.06 (-0.25, 0.38)	0.16	0.70
	Institution-based	Reference
	Population group
	Non-pregnant/non-lactating	-0.01 (-0.41, 0.41)	0.21	0.98
	Pregnant	-0.01 (-0.38, 0.35)	0.19	0.94
	WRA (unspecified)	Reference
	Sampling technique
	Non-probability	0.16 (-0.42, 0.10)	0.13	0.23
	Probability	Reference
	Laboratory assay
	Protein binding	0.19 (-0.11, 0.49)	0.15	0.21
	Microbiological	Reference
	Sample size
	<500	-0.12 (-0.38, 0.14)	0.13	0.34
	>500	Reference
	Mean age	-0.01 (-0.52, 0.04)	0.02	0.85

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Discussion

Given that there is a paucity of evidence on folate status, particularly in low-income countries [22], this systematic review and meta-analysis was a step towards estimating the pooled mean serum/plasma folate and prevalence of FD among WRA—a vulnerable population group—in Ethiopia, a low-income country. This will provide an essential step for policymakers and other stakeholders in designing, planning and implementing future context-specific interventions on folate.

Ten studies were eligible for this review; however, two [10, 51] were not considered in the meta-analyses. One of these two studies reported folate insufficiency instead of FD [10], and the other reported both possible/marginal FD and FD combined into one [51]. On the other hand, only two studies reported factors associated with FD. We did not perform a meta-analysis because iron deficiency anemia was the single factor reported in these studies [4, 52]. Therefore, we calculated pooled mean serum/plasma folate and pooled prevalence of FD from four [4, 27, 29, 52] and eight [4, 27–32, 52] studies, respectively.

The current meta-analysis revealed that the pooled mean serum/plasma folate estimate was 7.14 ng/ml (95% CI: 5.73, 8.54). It was significantly higher among studies that applied non-probability sampling and those conducted in 2015 or earlier. Besides, the meta-regression analysis showed that the non-probability sampling technique was significantly associated with the mean serum/plasma folate. Although there is no comparative meta-analysis, the mean serum/plasma folate was consistent with study findings from Nepal (5.9 ng/ml) [53], Georgia (7.2 ng/ml) [54], Iran (8.0 ng/ml) [55], Lebanon (8.4 ng/ml) [56] and Senegal (8.5 ng/ml) [24]. However, it was lower than the findings of various studies in different parts of the world, where the mean serum/plasma folate ranged from 8.6 ng/ml in Austria to 16.3 ng/ml in Ecuador [57–67]. On the other hand, it was slightly higher than one national study included in this meta-analysis (5.6 ng/ml) [4]. Additionally, it was higher than the findings of several studies, where the mean serum/plasma folate ranged from 2.3 ng/ml in Mongolia to 5.7 ng/ml in Turkey [23, 68–73].

The discrepancies in the mean serum/plasma folate could be due to the differences in socio-economic status, study scale, population group, study period, blood sample collection and storage method, the type of laboratory assay used, and eating habits. Our meta-analysis focused on one of the low income-countries (i.e., Ethiopia) with limited coverage and adherence to folic acid supplementation. Although mandatory folic acid fortification has been endorsed by the country [45], its translation into action has been limited. Contrary to our review, most other studies were primary studies (not meta-analyses) from middle- and high-income countries. Additionally, these middle- and high-income countries have better coverage and adherence to folic acid supplementation and long history of endorsing of mandatory folic acid fortification and effective implementation.

The other point is that different studies use different methods and procedures for blood sample collection and storage and laboratory analysis, such as laboratory assays. Folate results show poor comparability across the laboratory methods, sometimes even within the same analytical technique [74, 75]. A single assay with different calibrators and laboratory set-ups can even produce different results [22], making it challenging to compare folate concentrations across surveys.

Differences in dietary habits across communities, including fasting and folic acid supplementations, could also explain the discrepancies, as serum/plasma folate is easily affected by recent intake [76]. Serum folate concentrations are approximately 10% higher in nonfasting than in fasting persons, complicating sample collection in field studies [77].

A significant driver of much of the recent public health attention to the importance of folate has been the link to NTDs [16]. In light of this, our systematic review and meta-analysis highlighted that the pooled prevalence of FD was 20.80% (95% CI: 11.29, 32.27), which was four times higher than the threshold for a country-wide public health problem (i.e., greater than 5%) [16–19]. Therefore, FD is clearly a concern in Ethiopia. Furthermore, significant differences were observed in the sub-group analysis by population group and mean age of WRA; meaning the prevalence was higher among WRA (unclassified population group) than the non-pregnant/non-lactating and pregnant women. In addition, it was higher among women above 30 years. However, no covariate was significantly associated with FD.

The prevalence of FD in this meta-analysis was consistent with one systematic review and meta-analysis, which pooled 45 surveys conducted in 39 countries from 2000 to 2014. Only 11 surveys were from lower economic countries; the pooled FD was greater than 20% for most countries [22]. Likewise, it was consistent with a national survey report (17.3%) included in our meta-analysis. However, the prevalence was higher than two study findings reported from India, with an FD prevalence of 3.2% and 3.5% [60, 73] and another study from Belize (4.1%) [9]. On the contrary, the prevalence of FD was lower in our meta-analysis than in one primary study done in Senegal (54.8%) [24].

The differences in socio-economic and demographic characteristics, study scale, setting, period and population, laboratory methods, cut-offs, and feeding habits could explain the variations in the prevalence of FD. The three studies [9, 60, 73] with inconsistent findings with our meta-analysis were single (not meta-analyses). This could be explained by the fact that a single primary study may not be comparable with a meta-analysis, which results from statistical analysis of several studies. The other reason for the difference could be the differences in the study population. For example, the Indian studies focused only on pregnant women. In most settings, pregnant women have more access to folic acid supplementation than other sub-groups of WRA. On the other hand, Belize is an upper middle-income country, which adopted the mandatory folic acid fortification into wheat flour in 1998 [78], whereas Ethiopia adopted it in 2022 [45]. This could be why the prevalence of FD is much lower in Belize than in our meta-analysis. The prevalence of FD in the Senegalese study was far higher than in our meta-analysis. The target group in the Senegalese study was WRA, where 90.8% were not pregnant [24]. This means most do not have access to folic acid supplementation provided during pregnancy as part of antenatal care.

Most importantly, the differences in FD could be due to variations in laboratory assays, cut-offs, and dietary practices [22, 76]. Folate is not stable and is found in the body in numerous forms. Therefore the various assays have a different affinity to the different active forms of folate [22]. Furthermore, studies use different cut-off points depending on the type of indicator used to define FD. In our meta-analysis, the included studies used two sets of cut-offs, published by the WHO [47]. Therefore, folate status should be measured using a microbiological assay as recommended by the WHO that is consistent with regard to common reagents and protocols along with assay-matched cut-offs to define FD and insufficiency for appropriate comparisons across studies [47, 79].

The systematic review and meta-analysis findings can be used as input for policies and programs and a gateway for further epidemiological and nutritional studies and meta-analyses. However, the systematic review and meta-analysis has some limitations. For example we could not produce the pooled estimates for folate insufficiency (an indicator of the risk of NTDs) and factors associated with FD or insufficiency due to the scarcity of adequate primary studies. Additionally, we could not estimate the pooled mean or prevalence of FD using RBC folate, which reflects long-term folate status, because few studies used this biomarker. Moreover, using different laboratory assays may have under- or over-estimated the results.

Conclusions

The systematic review and meta-analysis highlighted that the pooled mean serum/plasma folate concentration among WRA was relatively low. Significant differences were observed in mean serum/plasma folate concentration depending on the sampling techniques used by the studies and the study period (survey year). The pooled prevalence of FD was reported in one-fifth of the WRA, indicating its public health significance in Ethiopia. There was a significant difference in the prevalence by population group and mean age of WRA.

Therefore, the Ethiopian health and nutrition policies should design and strengthen public health strategies to address FD among WRA. Since the magnitude of FD varies throughout the country, targeted interventions are required to address the deficiency. Public health messages should be disseminated through different platforms to improve women’s knowledge of folate, its deficiency, prevention strategies, and folate-rich foods. The availability of folate-rich foods should be ensured by improving production, processing, preservation, pricing, and marketing. Additionally, the consumption of folate-rich foods and folic acid supplementation with a particular focus on coverage and adherence should be strengthened. Preconception folic acid supplementation should also be considered to reduce NTDs. Folic acid fortification is considered one of the most successful public health initiatives to reduce NTDs and has been an effective intervention strategy in many countries. Thus, the government of Ethiopia, in collaboration with partners, should invest more in folic acid fortification. The mandatory folic acid fortification endorsed by the country should be transformed into action.

Supporting information

S1 Dataset. The dataset from which the results of the study were produced (STATA file).

(DTA)

Click here for additional data file.^{(30.7KB, dta)}

S1 Table. Risk of bias and quality assessment result of the included 10 studies using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Studies Reporting Prevalence Data, 2022.

(DOCX)

Click here for additional data file.^{(21.2KB, docx)}

S2 Table. PRISMA 2020 checklist.

(DOCX)

Click here for additional data file.^{(37.6KB, docx)}

S1 Text. Full search strategy of studies.

(DOCX)

Click here for additional data file.^{(27.4KB, docx)}

S2 Text. A copy of manuscript with track changes (copyedited for language errors).

(DOCX)

Click here for additional data file.^{(411.7KB, docx)}

Acknowledgments

The authors are grateful to Dr. Tara D’Ann Wilfong for her contribution in copyediting our manuscript for language usage, spelling and grammar.

Abbreviations

AJOL: African Journals Online
CI: Confidence Interval
CINAHL: Cumulative Index to Nursing and Allied Health Literature
FD: Folate Deficiency
GHDx: Global Health Data Exchange
IQR: Inter-quartile Range
NTD: Neural Tube Defect
RBC: Red Blood Cell
SD: Standard Deviation
VMNIS: Vitamin and Mineral Nutrition Information System
WHO: World Health Organization
WRA: Women of Reproductive Age

Data Availability

All relevant data are within the paper and its Supporting information files.

Funding Statement

The author(s) received no specific funding for this work.

References

1.Gazzali A.M., Lobry M., Colombeau L. et al. (2016). Stability of folic acid under several parameters. Eur J Pharm Sci 93, Suppl. 419–30. doi: 10.1016/j.ejps.2016.08.045 [DOI] [PubMed] [Google Scholar]
2.Cordero A.M., Crider K.S., Rogers L.M. et al. (2015). Optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects: World Health Organization guidelines. MMWR Morb Mortal Wkly Rep 64, Suppl. 15, 421–3. [PMC free article] [PubMed] [Google Scholar]
3.Green R. (2011). Indicators for assessing folate and vitamin B-12 status and for monitoring the efficacy of intervention strategies. Am J Clin Nutr 94, Suppl. 2, 666s–72s. doi: 10.3945/ajcn.110.009613 [DOI] [PMC free article] [PubMed] [Google Scholar]
4.Haidar J., Melaku U., and Pobocik R.S. (2010). Folate deficiency in women of reproductive age in nine administrative regions of Ethiopia: an emerging public health problem. South African Journal of Clinical Nutrition 23, Suppl. 3, 132–7. [Google Scholar]
5.Allen L.H. (2008). Causes of vitamin B12 and folate deficiency. Food Nutr Bull 29, Suppl. 2 Suppl, S20–37. doi: 10.1177/15648265080292S105 [DOI] [PubMed] [Google Scholar]
6.McNulty H. and Scott J.M. (2008). Intake and status of folate and related B-vitamins: considerations and challenges in achieving optimal status. Br J Nutr 99 Suppl 3, Suppl. S48–54. doi: 10.1017/S0007114508006855 [DOI] [PubMed] [Google Scholar]
7.Antony A.C. (2007). In utero physiology: role of folic acid in nutrient delivery and fetal development. Am J Clin Nutr 85, Suppl. 2, 598s–603s. doi: 10.1093/ajcn/85.2.598S [DOI] [PubMed] [Google Scholar]
8.McNulty H. (1995). Folate requirements for health in different population groups. Br J Biomed Sci 52, Suppl. 2, 110–9. [PubMed] [Google Scholar]
9.Abdelrahim II, Adam G.K., Mohmmed A.A. et al. (2009). Anaemia, folate and vitamin B12 deficiency among pregnant women in an area of unstable malaria transmission in eastern Sudan. Trans R Soc Trop Med Hyg 103, Suppl. 5, 493–6. doi: 10.1016/j.trstmh.2008.10.007 [DOI] [PubMed] [Google Scholar]
10.Adela, A., Seifu, D., Menon, M. et al. (2018). Assessment of RBC-folate level and other determinant factors of neural tube defect among first trimester pregnant women who attends antenatal care in Lideta and T/haimanot health centers, Addis Ababa, Ethiopia. Suppl. http://etd.aau.edu.et/handle/123456789/13438.
11.Handiso Y.H., Belachew T., Abuye C. et al. (2021). A community-based randomized controlled trial providing weekly iron-folic acid supplementation increased serum- ferritin, -folate and hemoglobin concentration of adolescent girls in southern Ethiopia. Sci Rep 11, Suppl. 1, 9646. doi: 10.1038/s41598-021-89115-5 [DOI] [PMC free article] [PubMed] [Google Scholar]
12.Institute of Medicine. (1998). Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B(6), Folate, Vitamin B(12), Pantothenic Acid, Biotin, and Choline. Suppl. [PubMed]
13.Winkels R.M., Brouwer I.A., Siebelink E. et al. (2007). Bioavailability of food folates is 80% of that of folic acid. Am J Clin Nutr 85, Suppl. 2, 465–73. doi: 10.1093/ajcn/85.2.465 [DOI] [PubMed] [Google Scholar]
14.Cusick S.E., Mei Z., Freedman D.S. et al. (2008). Unexplained decline in the prevalence of anemia among US children and women between 1988–1994 and 1999–2002. Am J Clin Nutr 88, Suppl. 6, 1611–7. doi: 10.3945/ajcn.2008.25926 [DOI] [PubMed] [Google Scholar]
15.FMOH. (2016). Guidelines for the Prevention and Control of Micronutrient Deficiencies in Ethiopia. Suppl. http://repository.iifphc.org/bitstream/handle/123456789/1027/Micronutrient%20guideline.pdf?sequence=1&isAllowed=y.
16.Bailey L.B., Stover P.J., McNulty H. et al. (2015). Biomarkers of Nutrition for Development-Folate Review. J Nutr 145, Suppl. 7, 1636s–1680s. doi: 10.3945/jn.114.206599 [DOI] [PMC free article] [PubMed] [Google Scholar]
17.McLean E., de Benoist B., and Allen L.H. (2008). Review of the magnitude of folate and vitamin B12 deficiencies worldwide. Food Nutr Bull 29, Suppl. 2 Suppl, S38–51. doi: 10.1177/15648265080292S107 [DOI] [PubMed] [Google Scholar]
18.World Health Organization and Organization., F.a.A. (2006). Guidelines on food fortification with micronutrients. Geneva, Switzerland: World Health Organization. Suppl.
19.de Benoist B. (2008). Conclusions of a WHO technical consultation on folate and vitamin B12 deficiencies. Food Nutr Bull. 29, Suppl. 2, S238–S244. doi: 10.1177/15648265080292S129 [DOI] [PubMed] [Google Scholar]
20.Harika R., Faber M., Samuel F. et al. (2017). Micronutrient Status and Dietary Intake of Iron, Vitamin A, Iodine, Folate and Zinc in Women of Reproductive Age and Pregnant Women in Ethiopia, Kenya, Nigeria and South Africa: A Systematic Review of Data from 2005 to 2015. 9, Suppl. 10, 1096. Available from: https://www.mdpi.com/2072-6643/9/10/1096. [DOI] [PMC free article] [PubMed] [Google Scholar]
21.Nunn R.L., Kehoe S.H., Chopra H. et al. (2019). Dietary micronutrient intakes among women of reproductive age in Mumbai slums. Eur J Clin Nutr 73, Suppl. 11, 1536–1545. doi: 10.1038/s41430-019-0429-6 [DOI] [PMC free article] [PubMed] [Google Scholar]
22.Rogers L.M., Cordero A.M., Pfeiffer C.M. et al. (2018). Global folate status in women of reproductive age: a systematic review with emphasis on methodological issues. Ann N Y Acad Sci 1431, Suppl. 1, 35–57. doi: 10.1111/nyas.13963 [DOI] [PMC free article] [PubMed] [Google Scholar]
23.Rohner F., Northrop-Clewes C., Tschannen A.B. et al. (2014). Prevalence and public health relevance of micronutrient deficiencies and undernutrition in pre-school children and women of reproductive age in Côte d’Ivoire, West Africa. Public Health Nutr 17, Suppl. 9, 2016–28. doi: 10.1017/s136898001300222x [DOI] [PMC free article] [PubMed] [Google Scholar]
24.Ndiaye N.F., Idohou-Dossou N., Diouf A. et al. (2018). Folate Deficiency and Anemia Among Women of Reproductive Age (15–49 Years) in Senegal: Results of a National Cross-Sectional Survey Food and Nutrition Bulletin 39, Suppl. 1, 65–74. doi: 10.1177/0379572117739063 [DOI] [PubMed] [Google Scholar]
25.Ouédraogo S., Koura G.K., Accrombessi M.M. et al. (2012). Maternal anemia at first antenatal visit: prevalence and risk factors in a malaria-endemic area in Benin. Am J Trop Med Hyg 87, Suppl. 3, 418–24. doi: 10.4269/ajtmh.2012.11-0706 [DOI] [PMC free article] [PubMed] [Google Scholar]
26.Mgamb E., Gura Z., Wanzala P. et al. (2017). Folate deficiency and utilization of folic acid fortified flour among pregnant women attending antenatal clinic at Pumwani Maternity Hospital, Kenya, 2015. Pan Afr Med J 28, Suppl. Suppl 1, 8. doi: 10.11604/pamj.supp.2017.28.1.9296 [DOI] [PMC free article] [PubMed] [Google Scholar]
27.Gibson R.S., Abebe Y., Stabler S. et al. (2008). Zinc, gravida, infection, and iron, but not vitamin B-12 or folate status, predict hemoglobin during pregnancy in Southern Ethiopia. J Nutr 138, Suppl. 3, 581–6. doi: 10.1093/jn/138.3.581 [DOI] [PMC free article] [PubMed] [Google Scholar]
28.Bromage S., Andersen C.T., Tadesse A.W. et al. (2021). The global diet quality score is associated with higher nutrient adequacy, mid-upper arm circumference, venous hemoglobin, and serum folate among urban and rural Ethiopian adults. J Nutr 151, Suppl. 130s–142s. doi: 10.1093/jn/nxab264 [DOI] [PMC free article] [PubMed] [Google Scholar]
29.Elema T.B., Yimam K.B., Waka F.C. et al. (2018). Folate and Vitamin B-12 status of anemic pregnant women and association to hemoglobin during antenatal care, 17–37 weeks in Ambo Hospital, Oromia, Ethiopia, a multi-regression analysis of socio-economic and serum folate and Vitamin B-12. J Nutr Hum Health 2, Suppl. 1, 28–34. [Google Scholar]
30.EPHI. (2016). Ethiopian National Micronutrient Survey Report. Suppl. https://www.exemplars.health/-/media/files/egh/resources/stunting/ethiopia/ethiopian-national-micronutrient-survey-report.pdf.
31.Bekele, H. and Baye, K. (2019). The relationship between dietary folate intakes and serum folate status of reproductive age women in West Gojam, Ethiopia. Suppl.
32.Mebratu, L. and Baye, K. (2016). Identification of risk factors for anemia on third trimester pregnant women West Showa Zone, Ambo, Ethiopia. Suppl. http://etd.aau.edu.et/handle/123456789/1527.
33.Siega-Riz A.M., Savitz D.A., Zeisel S.H. et al. (2004). Second trimester folate status and preterm birth. Am J Obstet Gynecol 191, Suppl. 6, 1851–7. doi: 10.1016/j.ajog.2004.07.076 [DOI] [PubMed] [Google Scholar]
34.Rodrigues H.G., Gubert M.B., and Santos L.M. (2015). Folic acid intake by pregnant women from Vale do Jequitinhonha, Brazil, and the contribution of fortified foods. Arch Latinoam Nutr 65, Suppl. 1, 27–35. [PubMed] [Google Scholar]
35.Arias L.D., Parra B.E., Muñoz A.M. et al. (2017). Study Exploring the Effects of Daily Supplementation with 400 μg of Folic Acid on the Nutritional Status of Folate in Women of Reproductive Age. Birth Defects Res 109, Suppl. 8, 564–573. doi: 10.1002/bdr2.1004 [DOI] [PubMed] [Google Scholar]
36.Centeno Tablante E., Pachón H., Guetterman H.M. et al. (2019). Fortification of wheat and maize flour with folic acid for population health outcomes. Cochrane Database Syst Rev 7, Suppl. 7, Cd012150. doi: 10.1002/14651858.CD012150.pub2 [DOI] [PMC free article] [PubMed] [Google Scholar]
37.Bulloch R.E., McCowan L.M.E., Thompson J.M.D. et al. (2019). Plasma folate and its association with folic acid supplementation, socio-demographic and lifestyle factors among New Zealand pregnant women. Br J Nutr 122, Suppl. 8, 910–918. doi: 10.1017/S0007114519001788 [DOI] [PubMed] [Google Scholar]
38.McNulty H., Ward M., Hoey L. et al. (2019). Addressing optimal folate and related B-vitamin status through the lifecycle: health impacts and challenges. Proc Nutr Soc 78, Suppl. 3, 449–462. doi: 10.1017/S0029665119000661 [DOI] [PubMed] [Google Scholar]
39.Bitew Z.W., Worku T., Alebel A. et al. (2020). Magnitude and Associated Factors of Neural Tube Defects in Ethiopia: A Systematic Review and Meta-Analysis. Glob Pediatr Health 7, Suppl. 2333794x20939423. doi: 10.1177/2333794X20939423 [DOI] [PMC free article] [PubMed] [Google Scholar]
40.Kibret K.T., Chojenta C., D’Arcy E. et al. (2019). Spatial distribution and determinant factors of anaemia among women of reproductive age in Ethiopia: a multilevel and spatial analysis. BMJ Open 9, Suppl. 4, e027276. doi: 10.1136/bmjopen-2018-027276 [DOI] [PMC free article] [PubMed] [Google Scholar]
41.Liu L., Oza S., Hogan D. et al. (2016). Global, regional, and national causes of under-5 mortality in 2000–15: an updated systematic analysis with implications for the Sustainable Development Goals. Lancet 388, Suppl. 10063, 3027–3035. doi: 10.1016/S0140-6736(16)31593-8 [DOI] [PMC free article] [PubMed] [Google Scholar]
42.Ganji V. and Kafai M.R. (2006). Population reference values for plasma total homocysteine concentrations in US adults after the fortification of cereals with folic acid. Am J Clin Nutr 84, Suppl. 5, 989–94. doi: 10.1093/ajcn/84.5.989 [DOI] [PubMed] [Google Scholar]
43.UNICEF, World Bank, World Food Program et al. (2016). Ethiopia National Micronutrient Survey Report. Suppl. 1–60. https://www.ephi.gov.et.
44.Federal Ministry of Health of Ethiopia, National guideline for control and prevention of micronutrient deficiencies. 2004, FMOH Addis Ababa.
45.The Ethiopian Standard Council. (2022). Endorsement of the mandatory fortification of edible oil and wheat flour with folic acid. Suppl. https://www.nutritionintl.org/news/all-news/government-endorses-mandatory-food-fortification-prevent-high-burden-neural-tube-defects-ethiopia.
46.Page M.J., McKenzie J.E., Bossuyt P.M. et al. (2021). The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. Syst Rev 10, Suppl. 1, 89. doi: 10.1186/s13643-021-01626-4 [DOI] [PMC free article] [PubMed] [Google Scholar]
47.WHO. (2015). Serum and red blood cell folate concentrations for assessing folate status in populations. Vitamin and Mineral Nutrition Information System. Geneva: World Health Organization. Suppl. http://apps.who.int/iris/bitstream/10665/162114/1/WHO_NMH_NHD_EPG_15.01.pdf?ua=1.
48.Munn Z., Moola S., Lisy K. et al. (2015). Methodological guidance for systematic reviews of observational epidemiological studies reporting prevalence and cumulative incidence data. Int J Evid Based Healthc 13, Suppl. 3, 147–53. doi: 10.1097/XEB.0000000000000054 [DOI] [PubMed] [Google Scholar]
49.DerSimonian R. and Laird N. (1986). Meta-analysis in clinical trials. Control Clin Trials 7, Suppl. 3, 177–88. doi: 10.1016/0197-2456(86)90046-2 [DOI] [PubMed] [Google Scholar]
50.Altman D.G. and Bland J.M. (2005). Standard deviations and standard errors. BMJ (Clinical research ed.) 331, Suppl. 7521, 903–903. doi: 10.1136/bmj.331.7521.903 Available from: https://pubmed.ncbi.nlm.nih.gov/16223828. [DOI] [PMC free article] [PubMed] [Google Scholar]
51.Kucha W., Seifu D., Tirsit A. et al. (2022). Folate, Vitamin B12, and Homocysteine Levels in Women With Neural Tube Defect-Affected Pregnancy in Addis Ababa, Ethiopia. Front Nutr 9, Suppl. 873900. doi: 10.3389/fnut.2022.873900 [DOI] [PMC free article] [PubMed] [Google Scholar]
52.Yusuf, N., Roba, H.S., and Roba, K.T. (2021). Prevalence of folate deficiency and associated factor among pregnant women in Haramaya District, Eastern Ethiopia Suppl. [DOI] [PMC free article] [PubMed]
53.Chandyo R.K., Ulak M., Sommerfelt H. et al. (2016). Nutritional Intake and Status of Cobalamin and Folate among Non-Pregnant Women of Reproductive Age in Bhaktapur, Nepal. Nutrients 8, Suppl. 6. doi: 10.3390/nu8060375 [DOI] [PMC free article] [PubMed] [Google Scholar]
54.Ministry of Health and Social Affairs (Georgia), National Centre for Disease Control and Public Health, and Georgia., U. (2010). Report of the 2009 Georgia National Nutrition Survey. Vilnius: United Nations Children’s Fund-Georgia. Suppl.
55.Abdollahi Z., Elmadfa I., and Djazayery A. (2011). Efficacy of flour fortification with folic acid in women of childbearing age in Iran. Ann. Nutr. Metab. 58, Suppl. 188–196. doi: 10.1159/000329726 [DOI] [PubMed] [Google Scholar]
56.Al Khatib L., Obeid O., and Sibai A.M. (2006). Folate deficiency is associated with nutritional anaemia in Lebanese women of childbearing age. Public Health Nutr. 9, Suppl. 921–927. doi: 10.1017/phn2005921 [DOI] [PubMed] [Google Scholar]
57.Institut fur Ernahrungswissenschaften Universitat Wien and Bundesministeriums fur Gesundheit. (2012). Osterreichischer ernahrungsbericht 2012 [Austrian nutrition report 2012]. Vienna: Federal Ministry of Health. Suppl.
58.Bates, B., Prentice, A., and Bates, C. (2015). National Diet and Nutrition Survey Rolling Progamme (NDNS RP). Supplementary report: blood folate results for the UK as a whole, Scotland, Northern Ireland (years 1 to 4 combined) and Wales (years 2 to 5 combined). Public Health England, London. Suppl.
59.Chen K.J., Pan W.H., and Lin Y.C. (2011). Status in the Taiwanese population aged 19 years and older from the Nutrition and Health Survey in Taiwan 1993–1996 to 2005–2008. Asia Pac. J. Clin. Nutr. 20, Suppl. 275–282. [PubMed] [Google Scholar]
60.Saxena V., Naithani M., and Singh R. (2017). Epidemiological determinants of Folate deficiency among pregnant women of district Dehradun. Clinical Epidemiology and Global Health 5, Suppl. 21–27. doi: http%3A//dx.doi.org/10.1016/j.cegh.2016.06.003 [Google Scholar]
61.Al-Dallal, Z.S. and Moosa, K. (2003). Impact of the national flour fortification program on the prevalence of iron deficiency and anemia among women at reproductive age in the Kingdom of Bahrain (first monitoring study). Ministry of Health, Juffair. Suppl.
62.Ministry of Health (Argentina). (2007). Encuesta Nacional de Nutricion y Salud (ENNyS) 2004–2005. Documento de Resultados [NationalHealth andNutrition Survey (ENNyS) 2004–2005. Results document]. Buenos Aires: Ministry of Health, Federal Health Plan. Suppl.
63.Shamah-Levy T., Villalpando S., and Mejia-Rodriguez F. (2015). Prevalence of iron, folate, and vitamin B12 deficiencies in 20 to 49 years old women: Ensanut 2012. Salud Pública Mex. 57, Suppl. 385–393. doi: 10.21149/spm.v57i5.7618 [DOI] [PubMed] [Google Scholar]
64.Schultz, J.T. and Vatucawaqa, P.T. (2012). Impact of iron fortified flour in child bearing age (CBA) women in Fiji, 2010 report. National Food and Nutrition Centre, Suva. Suppl.
65.University of Otago, M.o.H.N.Z. (2011). A focus on nutrition: key findings of the 2008/09 New Zealand Adult Nutrition Survey. Wellington: Ministry of Health. Suppl.
66.Australian Bureau of Statistics. (2013). Australian Health Survey: biomedical results for nutrients, 2011–12. Canberra: Australian Bureau of Statistics. Suppl.
67.Freire, W., Ramirez-Luzuriaga, M., and Belmont, P. (2014). Tomo I: Encuesta Nacional de Salud y Nutrición de la población ecuatoriana de cero a 59 años. ENSANUT-ECU 2012.Ministry of Public Health/National Institute of Statistics and Census, Quito. Suppl.
68.Bolormaa, N., Byambatogtoch, B., and Bates, J. (2003). Final report of a survey assessing the nutritional consequences of the dzud in Mongolia. Ulaan Baatar: Mongolia Ministry of Health. Suppl.
69.Gil-Prieto R., Hernández V., and Cano B. (2009). Plasma homocysteine in adolescents depends on the interaction between methylenetetrahydrofolate reductase genotype, lipids and folate: a seroepidemiological study. Nutr. Metab. 5, Suppl. 39. doi: 10.1186/1743-7075-6-39 [DOI] [PMC free article] [PubMed] [Google Scholar]
70.Ministry of Health and Sanitation (Sierra Leone), UNICEF, Helen Keller International et al. (2015). 2013 Sierra Leone Micronutrient Survey. Freetown: Ministry of Health and Sanitation. Suppl.
71.Ministry of Health (Azerbaijan), State Statistical Committee, and UNICEF-Azerbaijan. (2014). AzerbaijanNutrition Survey (AzNS) 2013. Baku: Ministry of Health. Suppl.
72.Oner N., Vatansever U., and Karasalihoglu S. (2006). The prevalence of folic acid deficiency among adolescent girls living in Edirne, Turkey. J. Adolesc. Health 38, Suppl. 599–606. doi: 10.1016/j.jadohealth.2005.03.027 [DOI] [PubMed] [Google Scholar]
73.Finkelstein J.L., Fothergill A., Johnson C.B. et al. (2021). Anemia and Vitamin B-12 and Folate Status in Women of Reproductive Age in Southern India: Estimating Population-Based Risk of Neural Tube Defects. Curr Dev Nutr 5, Suppl. 5, nzab069. doi: 10.1093/cdn/nzab069 [DOI] [PMC free article] [PubMed] [Google Scholar]
74.Gunter E.W., Bowman B.A., Caudill S.P. et al. (1996). Results of an international round robin for serum and whole-blood folate. Clin Chem 42, Suppl. 10, 1689–94. [PubMed] [Google Scholar]
75.Pfeiffer, C., Gunter, E., and Caudill, S. Comparison of serum and whole blood folate measurements in 12 laboratories: An international study. in Clinical Chemistry. 2001. Amer Assoc Clinical Chemistry 2101 L Street NW, Suite 202, Washington DC.
76.Sobczynska-Malefora A. and Harrington D.J. (2018). Laboratory assessment of folate (vitamin B9) status. J. Clin. Pathol. 71, Suppl. 949. doi: 10.1136/jclinpath-2018-205048 [DOI] [PubMed] [Google Scholar]
77.Haynes B.M., Pfeiffer C.M., Sternberg M.R. et al. (2013). Selected physiologic variables are weakly to moderately associated with 29 biomarkers of diet and nutrition, NHANES 2003–2006. J Nutr 143, Suppl. 6, 1001s–10s. doi: 10.3945/jn.112.172882 [DOI] [PMC free article] [PubMed] [Google Scholar]
78.World Health Organization. (1998). Global database on the implementation of nutrition action (GINA). Suppl. https://extranet.who.int/nutrition/gina/en/node/25831.
79.World Health Organization. (2015). Guideline: optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects. Geneva: World Health Organization. Suppl. [PubMed]

PLoS One. doi: 10.1371/journal.pone.0285281.r001

Decision Letter 0

Abdu Oumer

13 Feb 2023

PONE-D-22-30184Folate deficiency among women of reproductive age in Ethiopia: a systematic review and meta-analysisPLOS ONE

Dear Dr. Berhe,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

ACADEMIC EDITOR:Details comments are placed below for your action. Please kindly address all the major comments raised by the reviewers and the editor while submittig your manuscript. The manuscript has many major methodological flaws which need to be addressed while resubmission.

==============================

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After a period of initial checks and thorough peer review, we come up with the review result. The manuscript has a merit for publication but it has many technical and other major issues which need to be addressed during the revision. Once, you addressed the requested suggestions at satisfactory level, decision on the manuscript will be made.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

**********

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Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Dear Plos ONE team of editorials, thank you for the chance given to me to review a manuscript titled “Folate deficiency among women of reproductive age in Ethiopia: a systematic review and meta-analysis”. One third of global women experience iron deficiency anemia and the study will have a paramount importance for the design and implementation of appropriate public health interventions and will fill the gap of literature on the field. I should also appreciate that the study is well referenced. The following are my comments;

1. The criteria for the inclusion and exclusion of the articles should be refined and clear cut. The identified article for assessing (a) serum concentration (b) for assessing folate deficiency should go together

2. Have you included only Pregnant women or non-pregnant women or both? How many are institutional and how many are community based?

3. Are you studying for clinical or epidemiological significance or both or?

4. When do we say folate deficiency is called “major public health problem” globally and in Ethiopia?

5. In case when there is ambiguity between the two independent extractors who had decided?

6. Where are the other search engines like other Universities repository and Addis Ababa University and EPHA joint publication Ethiopian Journal of Health development and Jimma University’s Journal of Health Sciences…etc

7. Where is the sub-group analysis based on the age, residence, education status of the participants

8. The result and the discussion contents should contain what it tends to contain.

9. The recommendations are already under implementation. Hence, do you have other innovative recommendations drawn from your findings?

10. The language and the statistics need mainly refinement. The language needs major revision

Reviewer #2: It’s a well-written and interesting study.

Abstract

1. Include the full names of the following abbreviated databases, AJOL, VMNIS, GHDx

2. Right the full names of WHO

3. The recommendation should consider planned and implemented innervations aimed to reduce folate deficiency. The interventions you suggested are already within the government's focus. However, there are shortcomings in the coverage, translating fortification policies into actions. The recommendation should be rewritten in light of this.

Introduction

1. The introduction should clearly state why folate deficiency has been considered a public health problem, especially among women of reproductive age.

2. Mention what are the currently implemented (iron-folic acid supplementation) and planned interventions (fortification).

3. The last paragraph should be focused on folate deficiency only.

4. You have stated that “However, evidence on the prevalence of FD among WRA are not strong enough to the level policymakers could develop evidence-based intervention strategies in the country except for folic acid supplementation for pregnant women who visit health facilities for antenatal care follow-up.” However, the Ethiopian Standard Council endorsed the mandatory fortification of edible oil and wheat flour on 10th June 2022, with the currently available evidence. This seems to be in contradiction with your claim. In light of this rewrite the above-mentioned section. You can find this information through this link https://www.nutritionintl.org/news/all-news/government-endorses-mandatory-food-fortification-prevent-high-burden-neural-tube-defects-ethiopia

Method

Search strategy

1. It has been mentioned that Addis Ababa university instructional repositories have been used. This is a great approach to identifying unpublished studies. Makes sure that the thesis or dissertation you have identified has not been published and cross-check for duplication.

2. Other major national universities' institutional repositories and research institution repositories should also be included in the search strategy.

Eligibility criteria

3. Mention how studies from the same survey have been handled

4. In line 107 remove “NOT”, since you haven’t used this boolean operator in the search strategy

Result

5. in line 175 remove “Id”

6. summarise characteristics of studies and participants in table format

7. correct table 1, has been split into two places

8. Table 1 has been cited on line number 225, however, this paragraph is not related to the findings reported in table 1.

9. Throughout the manuscript replace “participants” with woman of reproductive age (WRA)

10. Table 1 has been cited on line number 277, however, this paragraph is not related to the findings reported in table 1

11. Perform a sub-group analysis based on the laboratory method used to asses folate concentration If adequate studies can be found within the subgroups.

12. Please include types of laboratory methods used to analyse folate concentration as a covariate in the meta-regression.

13. Discuss further the similarity and difference in mean serum folate concentration and folate deficiency with studies from other nations; explain the similarity and difference from the perspective of implemented interventions aimed at reducing folate deficiency.

14. From lines 391 to 393 you have stated that “All the included studies into the meta-analysis were cross-sectional, and temporal relationship could not be established between the covariates and the outcome variables”. Remove these statements as the aim of this systematic review and meta-analysis is not to establish causality or explore folate deficiency determinants.

15. You have mentioned that different laboratory assays are used. Discuss how the difference in laboratory assays used may affect your finding, and comparability of studies.

Conclusion

16. Rewrite the concussion making it clear and concise

17. In line 403 replace “women” with women of reproductive age

18. From lines 403-404 you have stated that “Additionally, the pooled prevalence of FD was reported in one-fifth of the women, indicating its public health significance in Ethiopia.”. It is also possible to justify why folate deficiency is public health problem from the perspective of neural tube defect

19. You have recommended multiple interventions targeting folate deficiency among these interventions fortification has been proven to be the most effective one. On your recommendation, more emphasis should be given to fortification interventions.

**********

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Reviewer #1: No

Reviewer #2: No

**********

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Attachment

Submitted filename: review.docx

Click here for additional data file.^{(17.6KB, docx)}

PLoS One. 2023 May 8;18(5):e0285281. doi: 10.1371/journal.pone.0285281.r002

Author response to Decision Letter 0

3 Apr 2023

1. Comments from the academic editor and responses

Comment-1: Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming.

Response: The revised manuscript has been modified to PLOS ONE's style

Comment-2: We suggest you thoroughly copyedit your manuscript for language usage, spelling, and grammar. Upon resubmission, please provide the following: the name of the colleague or the details of the professional service that edited your manuscript, a copy of your manuscript showing your changes by either highlighting them or using track changes (uploaded as a *supporting information* file), and a clean copy of the edited manuscript (uploaded as the new *manuscript* file)”

Response: We have made our manuscript be copyedited by a native American English speaker—Dr. Tara Wilfong (MD, MPH). She is an Associate Professor at Haramaya University. We indicated this in the acknowledgement section of the manuscript

Comment-3: Please include a separate caption for each figure in your manuscript.

Response: We accepted the comment, and we corrected it

Comment-4: Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly.

Response: The comment is accepted and corrected as per the request

2. Comments of reviewer #1 and responses

Comment-1: The criteria for the inclusion and exclusion of the articles should be refined and clear cut.

Response: We appreciated the comment and we modified it as per the recommendation

Comment-2: The identified article for assessing (a) serum concentration (b) for assessing folate deficiency should go together.

Response: The number of articles for serum concentration and folate deficiency are not the same because some studies report only mean serum folate, some report only folate deficiency, and others report both. That’s why the number of identified articles are not the same for the serum folate and folate deficiency.

Comment-3: Have you included only Pregnant women or non-pregnant women or both? How many are institutional and how many are community based?

Response: We included women of reproductive age in general (both pregnant and non-pregnant women). In the identified articles, some studies were done among pregnant women, some in non-pregnant and others generally in women of reproductive age without specifying as pregnant or non-pregnat. Regarding the study setting, six of the studies were community based, while four studies were institution based. These all are clearly indicated on page 9 of the manuscript.

Comment-4: Are you studying for clinical or epidemiological significance or both or?

Response: The significance of this study is mainy a baseline framework for epidemiological and nutritional researches. It could also be used by policy makers/programmers as an input in planning prevention programs against folate deficiency. This is indiated on page 21, the last paragraph of the discussion

Comment-5: When do we say folate deficiency is called “major public health problem” globally and in Ethiopia?

Response: To the best of our knowledge, clear threshold based on the prevalence of folate deficiency has not been established. This is due to the use of different analytical methods and different biomarker cutoff points, and lack population-based relevant data. However, it is considered as a public health problem because it results in serious consequences such as megaloblastic anemia and neural tube defects. Generally, prevalence of folate deficiency >5% is represents a threshold for country-wide public health problem (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478945/ and https://www.tandfonline.com/doi/abs/10.1080/16070658.2010.11734327). We revised the introduction part accordingly.

Comment-6: In case when there is ambiguity between the two independent extractors who had decided?

Response: It was resolved through discussions and consultations with a third author. This is indicated on page 7.

Comment-7: Where are the other search engines like other Universities repository and Addis Ababa University and EPHA joint publication Ethiopian Journal of Health development and Jimma University’s Journal of Health Sciences…etc

Response: Thank you for the comment. We tried to search the institutional repositories of universities including Addis Ababa University, Jimma University, Hawassa University, Haramaya University, Arbaminch University, University of Gondar, Bahir Dar University and Mekelle University. However, we could not get theses and dissertations on folate deficiency, except Addis Ababa University. Even the repositories of some universities were not active during the searching period (e.g. Haramaya University). Most of the theses we got from the other universities were on iron-folic acid supplementation adherence. This is why we included only Addis Ababa University in the review report. Now, we revised it as we also did the search for the other Universities.

Concerning the journals such as Ethiopian Journal of Health Development and Journal of Health Sciences, we do not search on each and every journal. Rather, we search on databases or platforms like PubMed, Google scholar, Embase, CINAHL, given that the journals are expected to be indexed or their articles are at least available online. There are hundreds of thousands of journals, if not millions, in the world. So, searching all these journals individually is difficult. What is recommended is to search on the indexing platforms/databases.

Comment-8: Where is the sub-group analysis based on the age, residence, education status of the participants?

Response: The sub-group analysis for mean age is indicated on page 16-17 (table 2). However, we did not do sub-group analysis for residence and education. Regarding residence, most of the studies did not report the variable (except one study). In addition, some of the studies were conducted in rural areas only and some were done only in urban areas. Others seem as they included urban and rural settings, but they did not report the variable residence in their result section. And we could not extract data that could be pooled up. We did not also extract data for the variable education. Although two studies did not report results for educational status, the issue is different from residence. Almost all of the studies used different categories for the variable “educational status.” Therefore, there were inconsistencies in the categories/responses among the studies. E.g. one study reported it as ‘illiterate and literate’, another study reported it as ‘formal education and no formal education’, other study reported it as ‘educated, read/write, and illiterate’, another study also reported as ‘cannot read/write, informal education and formal education’ and so on. It was difficult to pool up these different categories into one. E.g some of those under the category ‘no formal education’ could include those who are able to read/write from informal education (e.g. religious education) and illiterate ones

Comment-9: The result and the discussion contents should contain what it tends to contain.

Response: We accepted the comment and tried to revise accordingly

Comment-10: The recommendations are already under implementation. Hence, do you have other innovative recommendations drawn from your findings?

Response: We appreciated the comment and we revised it. We recommended the programs and strategies under implementation to be strengthened because there are problems in implementation. E.g. there is problem in folic acid supplementation coverage and adherence. There is also shortcoming in translating the fortification program into action. We have also recommended some additional interventions.

Comment-11: The language and the statistics need mainly refinement. The language needs major revision

Response: We revised for any inconsistencies and discrepancies in the document, including the statistics. Additionally, a native English speaker edited the document for language and editorial issues.

3. Comments of reviewer #2

Abstract

Comment-1: Include the full names of the following abbreviations: AJOL, VMNIS, GHDx, WHO

Response: We accepted the comment and corrected it accordingly

Comment-2: The recommendation should consider planned and implemented innervations aimed to reduce folate deficiency. The interventions you suggested are already within the government's focus. However, there are shortcomings in the coverage, translating fortification policies into actions. The recommendation should be rewritten in light of this.

Response: We revised it according to the advice

Introduction

Comment-1: The introduction should clearly state why folate deficiency has been considered a public

Response: We accepted your comment and revised it accordingly

Comment-2: Mention what are the currently implemented (iron-folic acid supplementation) and planned interventions (fortification).

Response: We revised it as per the comment

Comment-3: The last paragraph should be focused on folate deficiency only.

Response: Corrected accordingly

Comment-4: You have stated that “However, evidence on the prevalence of FD among WRA are not strong enough to the level policymakers could develop evidence-based intervention strategies in the country except for folic acid supplementation for pregnant women who visit health facilities for antenatal care follow-up.” However, the Ethiopian Standard Council endorsed the mandatory fortification of edible oil and wheat flour on 10th June 2022, with the currently available evidence. This seems to be in contradiction with your claim. In light of this rewrite the above-mentioned section.

Response: Thank you for the source, and we have re-written it as per your recommendation

Methods

Comment-1: It has been mentioned that Addis Ababa university instructional repositories have been used. This is a great approach to identifying unpublished studies. Makes sure that the thesis or dissertation you have identified has not been published and cross-check for duplication.

Response: We appreciate your concern, and we actually faced with such issues. One Masters thesis was found published, but we excluded the thesis and included the published one

Comment-2: Other major national universities' institutional repositories and research institution repositories should also be included in the search strategy.

Response: The comment is appreciated. We tried to search the institutional repositories of universities including Addis Ababa University, Jimma University, Hawassa University, Haramaya University, Arbaminch University, University of Gondar, Bahir Dar University and Mekelle University. However, we could not get theses and dissertations on folate deficiency, except Addis Ababa University. Even the repositories of some universities were not active during the searching period (e.g. Haramaya University). Most of the theses we got from the other universities were on iron-folic acid supplementation adherence. This is why we included only Addis Ababa University in the review report. Now, we have revised it as we also did the search for the other Universities. Additionally, we considered the institutional repositories of the research centers/institues such as the Ethiopian Public Health Institute (EPHI), Ethiopian Health and Nutrition Research Institute (EHNRI) and Ethiopian Nutrition Institute (ENI). However, we obtained only one study from the EPHI (i.e. Ethiopia National Micronutrient Survey, 2016), one of the studies included in the meta-analysis. This study was also found in the Global Health Data Exchange (GHDx), which has been mentioned in the manuscript as a separate database. We have revised our manuscript to indicate as we searched the websites and repositories of these research institutes.

Comment-3: Mention how studies from the same survey have been handled in the eligibility criteria

Response: We indicated in the respective section (page 6-7)

Comment-4: 4. In line 107 remove “NOT”, since you haven’t used this boolean operator in the search strategy

Response: We removed it

Results

Comment-1: In line 175 remove “Id”

Response: We removed it

Comment-2: Summarise characteristics of studies and participants in table format

Response: We summarized it in table form and labeled it ‘Table 1’

Comment-3: Correct table 1, has been split into two places

Response: Corrected

Comment-4: Table 1 has been cited on line number 225, however, this paragraph is not related to the findings reported in table 1.

Response: We appreciated for this critical comment and we corrected all the inconsistencies in the manuscript, including table 1. In the revised manuscript, this table is named ‘Table 2’

Comment-5: Throughout the manuscript replace “participants” with woman of reproductive age (WRA)

Response: Corrected

Comment-6: Table 1 has been cited on line number 277, however, this paragraph is not related to the findings reported in table 1

Response: We have corrected it

Comment-7: Perform a sub-group analysis based on the laboratory method used to asses folate concentration if adequate studies can be found within the subgroups

Response: The reason why we did not report on the sub-group analysis by laboratory method was due to inadequate studies for the microbiological assay (MBA) method.

Comment-8: Please include types of laboratory methods used to analyse folate concentration as a covariate in the meta-regression.

Response: We performed the analysis and included it as a covariate, but no significant association shown (table 3, page 20-21)

Comment-9: Discuss further the similarity and difference in mean serum folate concentration and folate deficiency with studies from other nations; explain the similarity and difference from the perspective of implemented interventions aimed at reducing folate deficiency.

Response: We tried to revise it accordingly

Comment-10: From lines 391 to 393 you have stated that “All the included studies into the meta-analysis were cross-sectional, and temporal relationship could not be established between the covariates and the outcome variables”. Remove these statements as the aim of this systematic review and meta-analysis is not to establish causality or explore folate deficiency determinants.

Response: We removed it

Comment-11: You have mentioned that different laboratory assays are used. Discuss how the difference in laboratory assays used may affect your finding, and comparability of studies.

Response: We have discussed it in bothe the mean and the prevalence

Conclusions

Comment-1: Rewrite the concussion making it clear and concise

Response: We did some modifications to make it clear

Comment-2: In line 403 replace “women” with women of reproductive age

Response: We have replaced it accordingly

Comment-3: From lines 403-404 you have stated that “Additionally, the pooled prevalence of FD was reported in one-fifth of the women, indicating its public health significance in Ethiopia.”. It is also possible to justify why folate deficiency is public health problem from the perspective of neural tube defect

Response: It could be justified, but as you said above, the main aim of the study is to assess the prevalence of folate deficiency. So, the conclusion should also be in line with the objective. We have already shown the public health significance of FD using the burden of NTDs in the introduction and discussion parts

Comment-4: You have recommended multiple interventions targeting folate deficiency among these interventions fortification has been proven to be the most effective one. On your recommendation, more emphasis should be given to fortification interventions.

Response: We have revised the recommendation based on the comment

===============End===============

Attachment

Submitted filename: Response to Reviewers.docx

Click here for additional data file.^{(39.4KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0285281.r003

Decision Letter 1

Abdu Oumer

19 Apr 2023

Folate deficiency among women of reproductive age in Ethiopia: a systematic review and meta-analysis

PONE-D-22-30184R1

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PLoS One. doi: 10.1371/journal.pone.0285281.r004

Acceptance letter

Abdu Oumer

25 Apr 2023

PONE-D-22-30184R1

Folate deficiency among women of reproductive age in Ethiopia: a systematic review and meta-analysis

Dear Dr. Gebremichael:

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Supplementary Materials

S1 Dataset. The dataset from which the results of the study were produced (STATA file).

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S1 Table. Risk of bias and quality assessment result of the included 10 studies using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Studies Reporting Prevalence Data, 2022.

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S2 Table. PRISMA 2020 checklist.

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S1 Text. Full search strategy of studies.

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S2 Text. A copy of manuscript with track changes (copyedited for language errors).

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Attachment

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Attachment

Submitted filename: Response to Reviewers.docx

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Data Availability Statement

All relevant data are within the paper and its Supporting information files.

[pone.0285281.ref001] 1.Gazzali A.M., Lobry M., Colombeau L. et al. (2016). Stability of folic acid under several parameters. Eur J Pharm Sci 93, Suppl. 419–30. doi: 10.1016/j.ejps.2016.08.045 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref002] 2.Cordero A.M., Crider K.S., Rogers L.M. et al. (2015). Optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects: World Health Organization guidelines. MMWR Morb Mortal Wkly Rep 64, Suppl. 15, 421–3. [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref003] 3.Green R. (2011). Indicators for assessing folate and vitamin B-12 status and for monitoring the efficacy of intervention strategies. Am J Clin Nutr 94, Suppl. 2, 666s–72s. doi: 10.3945/ajcn.110.009613 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref004] 4.Haidar J., Melaku U., and Pobocik R.S. (2010). Folate deficiency in women of reproductive age in nine administrative regions of Ethiopia: an emerging public health problem. South African Journal of Clinical Nutrition 23, Suppl. 3, 132–7. [Google Scholar]

[pone.0285281.ref005] 5.Allen L.H. (2008). Causes of vitamin B12 and folate deficiency. Food Nutr Bull 29, Suppl. 2 Suppl, S20–37. doi: 10.1177/15648265080292S105 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref006] 6.McNulty H. and Scott J.M. (2008). Intake and status of folate and related B-vitamins: considerations and challenges in achieving optimal status. Br J Nutr 99 Suppl 3, Suppl. S48–54. doi: 10.1017/S0007114508006855 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref007] 7.Antony A.C. (2007). In utero physiology: role of folic acid in nutrient delivery and fetal development. Am J Clin Nutr 85, Suppl. 2, 598s–603s. doi: 10.1093/ajcn/85.2.598S [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref008] 8.McNulty H. (1995). Folate requirements for health in different population groups. Br J Biomed Sci 52, Suppl. 2, 110–9. [PubMed] [Google Scholar]

[pone.0285281.ref009] 9.Abdelrahim II, Adam G.K., Mohmmed A.A. et al. (2009). Anaemia, folate and vitamin B12 deficiency among pregnant women in an area of unstable malaria transmission in eastern Sudan. Trans R Soc Trop Med Hyg 103, Suppl. 5, 493–6. doi: 10.1016/j.trstmh.2008.10.007 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref010] 10.Adela, A., Seifu, D., Menon, M. et al. (2018). Assessment of RBC-folate level and other determinant factors of neural tube defect among first trimester pregnant women who attends antenatal care in Lideta and T/haimanot health centers, Addis Ababa, Ethiopia. Suppl. http://etd.aau.edu.et/handle/123456789/13438.

[pone.0285281.ref011] 11.Handiso Y.H., Belachew T., Abuye C. et al. (2021). A community-based randomized controlled trial providing weekly iron-folic acid supplementation increased serum- ferritin, -folate and hemoglobin concentration of adolescent girls in southern Ethiopia. Sci Rep 11, Suppl. 1, 9646. doi: 10.1038/s41598-021-89115-5 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref012] 12.Institute of Medicine. (1998). Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B(6), Folate, Vitamin B(12), Pantothenic Acid, Biotin, and Choline. Suppl. [PubMed]

[pone.0285281.ref013] 13.Winkels R.M., Brouwer I.A., Siebelink E. et al. (2007). Bioavailability of food folates is 80% of that of folic acid. Am J Clin Nutr 85, Suppl. 2, 465–73. doi: 10.1093/ajcn/85.2.465 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref014] 14.Cusick S.E., Mei Z., Freedman D.S. et al. (2008). Unexplained decline in the prevalence of anemia among US children and women between 1988–1994 and 1999–2002. Am J Clin Nutr 88, Suppl. 6, 1611–7. doi: 10.3945/ajcn.2008.25926 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref015] 15.FMOH. (2016). Guidelines for the Prevention and Control of Micronutrient Deficiencies in Ethiopia. Suppl. http://repository.iifphc.org/bitstream/handle/123456789/1027/Micronutrient%20guideline.pdf?sequence=1&isAllowed=y.

[pone.0285281.ref016] 16.Bailey L.B., Stover P.J., McNulty H. et al. (2015). Biomarkers of Nutrition for Development-Folate Review. J Nutr 145, Suppl. 7, 1636s–1680s. doi: 10.3945/jn.114.206599 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref017] 17.McLean E., de Benoist B., and Allen L.H. (2008). Review of the magnitude of folate and vitamin B12 deficiencies worldwide. Food Nutr Bull 29, Suppl. 2 Suppl, S38–51. doi: 10.1177/15648265080292S107 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref018] 18.World Health Organization and Organization., F.a.A. (2006). Guidelines on food fortification with micronutrients. Geneva, Switzerland: World Health Organization. Suppl.

[pone.0285281.ref019] 19.de Benoist B. (2008). Conclusions of a WHO technical consultation on folate and vitamin B12 deficiencies. Food Nutr Bull. 29, Suppl. 2, S238–S244. doi: 10.1177/15648265080292S129 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref020] 20.Harika R., Faber M., Samuel F. et al. (2017). Micronutrient Status and Dietary Intake of Iron, Vitamin A, Iodine, Folate and Zinc in Women of Reproductive Age and Pregnant Women in Ethiopia, Kenya, Nigeria and South Africa: A Systematic Review of Data from 2005 to 2015. 9, Suppl. 10, 1096. Available from: https://www.mdpi.com/2072-6643/9/10/1096. [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref021] 21.Nunn R.L., Kehoe S.H., Chopra H. et al. (2019). Dietary micronutrient intakes among women of reproductive age in Mumbai slums. Eur J Clin Nutr 73, Suppl. 11, 1536–1545. doi: 10.1038/s41430-019-0429-6 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref022] 22.Rogers L.M., Cordero A.M., Pfeiffer C.M. et al. (2018). Global folate status in women of reproductive age: a systematic review with emphasis on methodological issues. Ann N Y Acad Sci 1431, Suppl. 1, 35–57. doi: 10.1111/nyas.13963 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref023] 23.Rohner F., Northrop-Clewes C., Tschannen A.B. et al. (2014). Prevalence and public health relevance of micronutrient deficiencies and undernutrition in pre-school children and women of reproductive age in Côte d’Ivoire, West Africa. Public Health Nutr 17, Suppl. 9, 2016–28. doi: 10.1017/s136898001300222x [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref024] 24.Ndiaye N.F., Idohou-Dossou N., Diouf A. et al. (2018). Folate Deficiency and Anemia Among Women of Reproductive Age (15–49 Years) in Senegal: Results of a National Cross-Sectional Survey Food and Nutrition Bulletin 39, Suppl. 1, 65–74. doi: 10.1177/0379572117739063 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref025] 25.Ouédraogo S., Koura G.K., Accrombessi M.M. et al. (2012). Maternal anemia at first antenatal visit: prevalence and risk factors in a malaria-endemic area in Benin. Am J Trop Med Hyg 87, Suppl. 3, 418–24. doi: 10.4269/ajtmh.2012.11-0706 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref026] 26.Mgamb E., Gura Z., Wanzala P. et al. (2017). Folate deficiency and utilization of folic acid fortified flour among pregnant women attending antenatal clinic at Pumwani Maternity Hospital, Kenya, 2015. Pan Afr Med J 28, Suppl. Suppl 1, 8. doi: 10.11604/pamj.supp.2017.28.1.9296 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref027] 27.Gibson R.S., Abebe Y., Stabler S. et al. (2008). Zinc, gravida, infection, and iron, but not vitamin B-12 or folate status, predict hemoglobin during pregnancy in Southern Ethiopia. J Nutr 138, Suppl. 3, 581–6. doi: 10.1093/jn/138.3.581 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref028] 28.Bromage S., Andersen C.T., Tadesse A.W. et al. (2021). The global diet quality score is associated with higher nutrient adequacy, mid-upper arm circumference, venous hemoglobin, and serum folate among urban and rural Ethiopian adults. J Nutr 151, Suppl. 130s–142s. doi: 10.1093/jn/nxab264 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref029] 29.Elema T.B., Yimam K.B., Waka F.C. et al. (2018). Folate and Vitamin B-12 status of anemic pregnant women and association to hemoglobin during antenatal care, 17–37 weeks in Ambo Hospital, Oromia, Ethiopia, a multi-regression analysis of socio-economic and serum folate and Vitamin B-12. J Nutr Hum Health 2, Suppl. 1, 28–34. [Google Scholar]

[pone.0285281.ref030] 30.EPHI. (2016). Ethiopian National Micronutrient Survey Report. Suppl. https://www.exemplars.health/-/media/files/egh/resources/stunting/ethiopia/ethiopian-national-micronutrient-survey-report.pdf.

[pone.0285281.ref031] 31.Bekele, H. and Baye, K. (2019). The relationship between dietary folate intakes and serum folate status of reproductive age women in West Gojam, Ethiopia. Suppl.

[pone.0285281.ref032] 32.Mebratu, L. and Baye, K. (2016). Identification of risk factors for anemia on third trimester pregnant women West Showa Zone, Ambo, Ethiopia. Suppl. http://etd.aau.edu.et/handle/123456789/1527.

[pone.0285281.ref033] 33.Siega-Riz A.M., Savitz D.A., Zeisel S.H. et al. (2004). Second trimester folate status and preterm birth. Am J Obstet Gynecol 191, Suppl. 6, 1851–7. doi: 10.1016/j.ajog.2004.07.076 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref034] 34.Rodrigues H.G., Gubert M.B., and Santos L.M. (2015). Folic acid intake by pregnant women from Vale do Jequitinhonha, Brazil, and the contribution of fortified foods. Arch Latinoam Nutr 65, Suppl. 1, 27–35. [PubMed] [Google Scholar]

[pone.0285281.ref035] 35.Arias L.D., Parra B.E., Muñoz A.M. et al. (2017). Study Exploring the Effects of Daily Supplementation with 400 μg of Folic Acid on the Nutritional Status of Folate in Women of Reproductive Age. Birth Defects Res 109, Suppl. 8, 564–573. doi: 10.1002/bdr2.1004 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref036] 36.Centeno Tablante E., Pachón H., Guetterman H.M. et al. (2019). Fortification of wheat and maize flour with folic acid for population health outcomes. Cochrane Database Syst Rev 7, Suppl. 7, Cd012150. doi: 10.1002/14651858.CD012150.pub2 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref037] 37.Bulloch R.E., McCowan L.M.E., Thompson J.M.D. et al. (2019). Plasma folate and its association with folic acid supplementation, socio-demographic and lifestyle factors among New Zealand pregnant women. Br J Nutr 122, Suppl. 8, 910–918. doi: 10.1017/S0007114519001788 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref038] 38.McNulty H., Ward M., Hoey L. et al. (2019). Addressing optimal folate and related B-vitamin status through the lifecycle: health impacts and challenges. Proc Nutr Soc 78, Suppl. 3, 449–462. doi: 10.1017/S0029665119000661 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref039] 39.Bitew Z.W., Worku T., Alebel A. et al. (2020). Magnitude and Associated Factors of Neural Tube Defects in Ethiopia: A Systematic Review and Meta-Analysis. Glob Pediatr Health 7, Suppl. 2333794x20939423. doi: 10.1177/2333794X20939423 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref040] 40.Kibret K.T., Chojenta C., D’Arcy E. et al. (2019). Spatial distribution and determinant factors of anaemia among women of reproductive age in Ethiopia: a multilevel and spatial analysis. BMJ Open 9, Suppl. 4, e027276. doi: 10.1136/bmjopen-2018-027276 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref041] 41.Liu L., Oza S., Hogan D. et al. (2016). Global, regional, and national causes of under-5 mortality in 2000–15: an updated systematic analysis with implications for the Sustainable Development Goals. Lancet 388, Suppl. 10063, 3027–3035. doi: 10.1016/S0140-6736(16)31593-8 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref042] 42.Ganji V. and Kafai M.R. (2006). Population reference values for plasma total homocysteine concentrations in US adults after the fortification of cereals with folic acid. Am J Clin Nutr 84, Suppl. 5, 989–94. doi: 10.1093/ajcn/84.5.989 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref043] 43.UNICEF, World Bank, World Food Program et al. (2016). Ethiopia National Micronutrient Survey Report. Suppl. 1–60. https://www.ephi.gov.et.

[pone.0285281.ref044] 44.Federal Ministry of Health of Ethiopia, National guideline for control and prevention of micronutrient deficiencies. 2004, FMOH Addis Ababa.

[pone.0285281.ref045] 45.The Ethiopian Standard Council. (2022). Endorsement of the mandatory fortification of edible oil and wheat flour with folic acid. Suppl. https://www.nutritionintl.org/news/all-news/government-endorses-mandatory-food-fortification-prevent-high-burden-neural-tube-defects-ethiopia.

[pone.0285281.ref046] 46.Page M.J., McKenzie J.E., Bossuyt P.M. et al. (2021). The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. Syst Rev 10, Suppl. 1, 89. doi: 10.1186/s13643-021-01626-4 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref047] 47.WHO. (2015). Serum and red blood cell folate concentrations for assessing folate status in populations. Vitamin and Mineral Nutrition Information System. Geneva: World Health Organization. Suppl. http://apps.who.int/iris/bitstream/10665/162114/1/WHO_NMH_NHD_EPG_15.01.pdf?ua=1.

[pone.0285281.ref048] 48.Munn Z., Moola S., Lisy K. et al. (2015). Methodological guidance for systematic reviews of observational epidemiological studies reporting prevalence and cumulative incidence data. Int J Evid Based Healthc 13, Suppl. 3, 147–53. doi: 10.1097/XEB.0000000000000054 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref049] 49.DerSimonian R. and Laird N. (1986). Meta-analysis in clinical trials. Control Clin Trials 7, Suppl. 3, 177–88. doi: 10.1016/0197-2456(86)90046-2 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref050] 50.Altman D.G. and Bland J.M. (2005). Standard deviations and standard errors. BMJ (Clinical research ed.) 331, Suppl. 7521, 903–903. doi: 10.1136/bmj.331.7521.903 Available from: https://pubmed.ncbi.nlm.nih.gov/16223828. [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref051] 51.Kucha W., Seifu D., Tirsit A. et al. (2022). Folate, Vitamin B12, and Homocysteine Levels in Women With Neural Tube Defect-Affected Pregnancy in Addis Ababa, Ethiopia. Front Nutr 9, Suppl. 873900. doi: 10.3389/fnut.2022.873900 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref052] 52.Yusuf, N., Roba, H.S., and Roba, K.T. (2021). Prevalence of folate deficiency and associated factor among pregnant women in Haramaya District, Eastern Ethiopia Suppl. [DOI] [PMC free article] [PubMed]

[pone.0285281.ref053] 53.Chandyo R.K., Ulak M., Sommerfelt H. et al. (2016). Nutritional Intake and Status of Cobalamin and Folate among Non-Pregnant Women of Reproductive Age in Bhaktapur, Nepal. Nutrients 8, Suppl. 6. doi: 10.3390/nu8060375 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref054] 54.Ministry of Health and Social Affairs (Georgia), National Centre for Disease Control and Public Health, and Georgia., U. (2010). Report of the 2009 Georgia National Nutrition Survey. Vilnius: United Nations Children’s Fund-Georgia. Suppl.

[pone.0285281.ref055] 55.Abdollahi Z., Elmadfa I., and Djazayery A. (2011). Efficacy of flour fortification with folic acid in women of childbearing age in Iran. Ann. Nutr. Metab. 58, Suppl. 188–196. doi: 10.1159/000329726 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref056] 56.Al Khatib L., Obeid O., and Sibai A.M. (2006). Folate deficiency is associated with nutritional anaemia in Lebanese women of childbearing age. Public Health Nutr. 9, Suppl. 921–927. doi: 10.1017/phn2005921 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref057] 57.Institut fur Ernahrungswissenschaften Universitat Wien and Bundesministeriums fur Gesundheit. (2012). Osterreichischer ernahrungsbericht 2012 [Austrian nutrition report 2012]. Vienna: Federal Ministry of Health. Suppl.

[pone.0285281.ref058] 58.Bates, B., Prentice, A., and Bates, C. (2015). National Diet and Nutrition Survey Rolling Progamme (NDNS RP). Supplementary report: blood folate results for the UK as a whole, Scotland, Northern Ireland (years 1 to 4 combined) and Wales (years 2 to 5 combined). Public Health England, London. Suppl.

[pone.0285281.ref059] 59.Chen K.J., Pan W.H., and Lin Y.C. (2011). Status in the Taiwanese population aged 19 years and older from the Nutrition and Health Survey in Taiwan 1993–1996 to 2005–2008. Asia Pac. J. Clin. Nutr. 20, Suppl. 275–282. [PubMed] [Google Scholar]

[pone.0285281.ref060] 60.Saxena V., Naithani M., and Singh R. (2017). Epidemiological determinants of Folate deficiency among pregnant women of district Dehradun. Clinical Epidemiology and Global Health 5, Suppl. 21–27. doi: http%3A//dx.doi.org/10.1016/j.cegh.2016.06.003 [Google Scholar]

[pone.0285281.ref061] 61.Al-Dallal, Z.S. and Moosa, K. (2003). Impact of the national flour fortification program on the prevalence of iron deficiency and anemia among women at reproductive age in the Kingdom of Bahrain (first monitoring study). Ministry of Health, Juffair. Suppl.

[pone.0285281.ref062] 62.Ministry of Health (Argentina). (2007). Encuesta Nacional de Nutricion y Salud (ENNyS) 2004–2005. Documento de Resultados [NationalHealth andNutrition Survey (ENNyS) 2004–2005. Results document]. Buenos Aires: Ministry of Health, Federal Health Plan. Suppl.

[pone.0285281.ref063] 63.Shamah-Levy T., Villalpando S., and Mejia-Rodriguez F. (2015). Prevalence of iron, folate, and vitamin B12 deficiencies in 20 to 49 years old women: Ensanut 2012. Salud Pública Mex. 57, Suppl. 385–393. doi: 10.21149/spm.v57i5.7618 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref064] 64.Schultz, J.T. and Vatucawaqa, P.T. (2012). Impact of iron fortified flour in child bearing age (CBA) women in Fiji, 2010 report. National Food and Nutrition Centre, Suva. Suppl.

[pone.0285281.ref065] 65.University of Otago, M.o.H.N.Z. (2011). A focus on nutrition: key findings of the 2008/09 New Zealand Adult Nutrition Survey. Wellington: Ministry of Health. Suppl.

[pone.0285281.ref066] 66.Australian Bureau of Statistics. (2013). Australian Health Survey: biomedical results for nutrients, 2011–12. Canberra: Australian Bureau of Statistics. Suppl.

[pone.0285281.ref067] 67.Freire, W., Ramirez-Luzuriaga, M., and Belmont, P. (2014). Tomo I: Encuesta Nacional de Salud y Nutrición de la población ecuatoriana de cero a 59 años. ENSANUT-ECU 2012.Ministry of Public Health/National Institute of Statistics and Census, Quito. Suppl.

[pone.0285281.ref068] 68.Bolormaa, N., Byambatogtoch, B., and Bates, J. (2003). Final report of a survey assessing the nutritional consequences of the dzud in Mongolia. Ulaan Baatar: Mongolia Ministry of Health. Suppl.

[pone.0285281.ref069] 69.Gil-Prieto R., Hernández V., and Cano B. (2009). Plasma homocysteine in adolescents depends on the interaction between methylenetetrahydrofolate reductase genotype, lipids and folate: a seroepidemiological study. Nutr. Metab. 5, Suppl. 39. doi: 10.1186/1743-7075-6-39 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref070] 70.Ministry of Health and Sanitation (Sierra Leone), UNICEF, Helen Keller International et al. (2015). 2013 Sierra Leone Micronutrient Survey. Freetown: Ministry of Health and Sanitation. Suppl.

[pone.0285281.ref071] 71.Ministry of Health (Azerbaijan), State Statistical Committee, and UNICEF-Azerbaijan. (2014). AzerbaijanNutrition Survey (AzNS) 2013. Baku: Ministry of Health. Suppl.

[pone.0285281.ref072] 72.Oner N., Vatansever U., and Karasalihoglu S. (2006). The prevalence of folic acid deficiency among adolescent girls living in Edirne, Turkey. J. Adolesc. Health 38, Suppl. 599–606. doi: 10.1016/j.jadohealth.2005.03.027 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref073] 73.Finkelstein J.L., Fothergill A., Johnson C.B. et al. (2021). Anemia and Vitamin B-12 and Folate Status in Women of Reproductive Age in Southern India: Estimating Population-Based Risk of Neural Tube Defects. Curr Dev Nutr 5, Suppl. 5, nzab069. doi: 10.1093/cdn/nzab069 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref074] 74.Gunter E.W., Bowman B.A., Caudill S.P. et al. (1996). Results of an international round robin for serum and whole-blood folate. Clin Chem 42, Suppl. 10, 1689–94. [PubMed] [Google Scholar]

[pone.0285281.ref075] 75.Pfeiffer, C., Gunter, E., and Caudill, S. Comparison of serum and whole blood folate measurements in 12 laboratories: An international study. in Clinical Chemistry. 2001. Amer Assoc Clinical Chemistry 2101 L Street NW, Suite 202, Washington DC.

[pone.0285281.ref076] 76.Sobczynska-Malefora A. and Harrington D.J. (2018). Laboratory assessment of folate (vitamin B9) status. J. Clin. Pathol. 71, Suppl. 949. doi: 10.1136/jclinpath-2018-205048 [DOI] [PubMed] [Google Scholar]

[pone.0285281.ref077] 77.Haynes B.M., Pfeiffer C.M., Sternberg M.R. et al. (2013). Selected physiologic variables are weakly to moderately associated with 29 biomarkers of diet and nutrition, NHANES 2003–2006. J Nutr 143, Suppl. 6, 1001s–10s. doi: 10.3945/jn.112.172882 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0285281.ref078] 78.World Health Organization. (1998). Global database on the implementation of nutrition action (GINA). Suppl. https://extranet.who.int/nutrition/gina/en/node/25831.

[pone.0285281.ref079] 79.World Health Organization. (2015). Guideline: optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects. Geneva: World Health Organization. Suppl. [PubMed]

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Folate deficiency among women of reproductive age in Ethiopia: A systematic review and meta-analysis

Berhe Gebremichael

Hirbo Shore Roba

Alemeshet Getachew

Dejene Tesfaye

Haftu Asmerom

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Abstract

Background

Methods

Results

Conclusions

Systematic review registration

Introduction

Methods and materials

Registration

Search strategy

Eligibility criteria

Study risk of bias and quality assessment

Data collection (extraction) process

Data synthesis and analysis

Ethics statement

Results

Study selection process

Fig 1. PRISMA flow diagram showing the selection process of studies for the systematic review and meta-analysis on folate deficiency among women of reproductive age in Ethiopia, 2022.

Characteristics of included studies

Table 1. Summary characteristics of the 10 studies included in the systematic review and meta-analysis of folate deficiency among women of reproductive age in Ethiopia, 2022.

Risk of bias and quality assessment

Mean serum/plasma folate concentration

Fig 2. Forest plot of mean serum/plasma folate level among women of reproductive age in Ethiopia, 2022.

Prevalence of folate deficiency

Fig 3. Forest plot of the prevalence of folate deficiency among women of reproductive age in Ethiopia, 2022.

Subgroup analysis for mean serum/plasma folate concentration

Fig 4. Forest plot of subgroup analysis for mean serum/plasma folate level by survey year among women of reproductive age in Ethiopia, 2022.

Fig 5. Forest plot of subgroup analysis for mean serum/plasma folate level by sampling technique among women of reproductive age in Ethiopia, 2022.

Subgroup analysis for the prevalence of folate deficiency

Fig 6. Forest plot of subgroup analysis for the prevalence of folate deficiency by population group among women of reproductive age in Ethiopia, 2022.

Fig 7. Forest plot of subgroup analysis for the prevalence of folate deficiency by mean age among women of reproductive age in Ethiopia, 2022.

Sensitivity analysis

Table 2. Leave-one-out sensitivity analysis showing the influence of each individual study on the overall estimate in the mean serum/plasma folate level (n = 4) and the prevalence of folate deficiency (n = 8) among women of reproductive age in Ethiopia, 2022.

Meta-regression

Table 3. Meta-regression result of covariates to explain heterogeneity observed in the mean serum/plasma folate level (n = 4) and folate deficiency (n = 8) among women of reproductive age in Ethiopia, 2022.

Discussion

Conclusions

Supporting information

Acknowledgments

Abbreviations

Data Availability

Funding Statement

References

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Author response to Decision Letter 0

Decision Letter 1

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Acceptance letter

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Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

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