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. 2021 Feb 16;16(2):e0247106. doi: 10.1371/journal.pone.0247106

Availability of adequately iodized salt at the household level in Ethiopia: A systematic review and meta-analysis

Alehegn Aderaw Alamneh 1,*, Cheru Tesema Leshargie 2,3, Melaku Desta 4, Molla Yigzaw Birhanu 5, Moges Agazhe Assemie 2, Habtamu Temesgen Denekew 1, Yoseph Merkeb Alamneh 6, Daniel Bekele Ketema 2
Editor: Shaun Wen Huey Lee7
PMCID: PMC7886221  PMID: 33592066

Abstract

Background

Iodine deficiency disorder (IDD) is a global, regional, and national public health problem that is preventable. Universal salt iodization is a worldwide accepted strategy to prevent IDD. The level of iodine in the salt should be adequate at the household level (≥15ppm). Though there was fragmented evidence on the proportion of adequately iodized salt at the household level in Ethiopia, the national level proportion of adequately iodized salt at the household level was remaining unknown. Therefore, this systematic review and meta-analysis estimated the pooled proportion of adequately iodized salt at the household level in Ethiopia from 2013–2020.

Method

We systematically searched the databases: PubMed/MEDLINE, Google Scholar, and Science Direct for studies conducted in Ethiopia on the availability of adequately iodized salt at the household level since 2013. We have included observational studies, which were published between January first, 2013, and 10 August 2020. The report was compiled according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The quality of included studies was scored based on the Newcastle Ottawa quality assessment scale adapted for cross-sectional studies. The data were extracted in Microsoft excel and analyzed using Stata version 14.1 software. We employed a random-effects model to estimate the pooled proportion of adequately iodized salt at the household level in Ethiopia. The presence of statistical heterogeneity within the included studies was evaluated using the I-squared statistic. We used Egger’s regression test to identify evidence of publication bias. The pooled proportion with a 95% confidence interval (CI) was presented using tables and forest plots.

Results

We screened a total of 195 articles. Of these, 28 studies (with 15561 households) were included in the final systematic review and meta-analysis. In Ethiopia, the pooled proportion of adequately iodized salt at the household level was 37% (95% CI: 28, 46%). The subgroup analyses of 28 studies by residence revealed that the pooled proportion of adequately iodized salt at the household level was 32% (95% CI: 29, 35%) and 48% (95% CI: 31, 66%) in rural and urban areas, respectively. Based on geographic location, the highest proportion was found in Addis Ababa (81%; 95%CI: 78, 83), and the lowest proportion found in Dire Dawa (20%; 95%CI: 17, 22). Besides, the proportion of adequately iodized salt at the household level was significantly increased during 2017–2020 (42%; 95% CI: 30, 53%) as compared with 2013–2016 (27%; 95% CI: 17, 39%).

Conclusions

In Ethiopia, the pooled proportion of adequately iodized salt at the household level was very low as compared to the world health organization’s recommendation. Thus, the Federal Ministry of Health of Ethiopia and different stakeholders should give more attention to improve the proportion of adequately iodized salt at the household level.

Background

Iodine is a chemical element that is essential for the synthesis of thyroid hormone by the thyroid gland in the body. Thyroid hormones are essential for the normal development and function of the brain and nervous system, and the maintenance of body heat and energy. When people do not have enough iodine, they cannot make enough thyroid hormone. This deficiency of iodine has several important health consequences that together are called iodine deficiency disorders (IDD). Iodine deficiency frequently causes permanent brain damage and cognitive impairment in children, reproductive failure (miscarriages, stillbirths), decreased child survival, goiter, and socioeconomic stagnation. Iodine deficiency is important because of its widespread prevalence and its destructive effects on human health. Proper supplementation with iodine completely prevents these consequences. Iodine is supplemented in the form of iodized salt, iodized oil, iodized water, and frequent administration of Lugol’s iodine. Among these, salt iodization has been proven and the most effective strategy to prevent IDD at the population level [1, 2].

Iodine deficiency is also a public health important problem in Ethiopia. The national total goiter rate among Ethiopian women was above 35.8% [3]. Also, the pooled estimate of goiter among children in Ethiopia was 40.50% Thus, the government of Ethiopia recommended and implemented universal salt iodization (USI) to prevent iodine deficiency and its associated deficiency disorders [4, 5]. The availability of adequately iodized salt at the household level is one of the process indicators used to monitor the consumption of iodized salt at the population level. According to the World Health Organization recommendation, the coverage of adequately iodized salt at the household level should be above 90% to prevent iodine deficiency disorders [2].

In Ethiopia, the proportion of adequately iodized salt at the household level has been reported in several studies, which is inconsistent and ranges from 4.6% at Dega Damot Districts of Amhara region [6] to 95.5% at Kolfe Keranio sub-city of Addis Ababa [7]. As a result of variations of findings across previously existing studies, producing a pooled proportion of adequately iodized salt at the household level is needed. Therefore, this systematic review and meta-analysis were conducted to produce the pooled proportion of adequately iodized salt at the household level in Ethiopia since 2013. The pooled estimate of adequately iodized salt at the household level will be an important indicator for the government, programmers, policymakers, and different stakeholders to monitor the progress of adequately iodized salt coverage at the household level.

Methods

Data source and search strategy

The studies were found through internet searches using databases of PubMed, Google Scholar, and Science direct. Searching of the articles was done by AAA, DBK, MD, CTL, MAA, MYB & HTD using the keywords of “Availability”, "Adequately Iodized salt" "Household Level" "Ethiopia" in combination or individually. The last search was conducted on 10 August 2020.

Inclusion criteria

Study setting

Studies conducted in Ethiopia were included.

Study units

Studies conducted on the availability of adequately iodized salt at the household’s level.

Publication status

Both published and unpublished articles were included.

Language

Only studies published in the English language were included.

Study type

Studies employed using observational study designs were included.

Publication year

Articles that were published between first January 2013 and 10th August 2020 were included. The rationale for including those studies published since January 2013 was to generate more recent information that will be useful for decision making.

Type of article

Only full-text articles were included.

Exclusion criteria

Studies that did not report the outcome of interest and studies with the unsatisfactory quality score (Newcastle Ottawa quality score ≤4) were excluded from this systematic review and meta-analysis [8].

Screening, data extraction, and quality assessment

Before conducting data abstraction, the data extraction format was prepared in a Microsoft™ Excel spreadsheet. The data extraction sheet includes the author’s name, year of publication, study design, region, study area, residence sample size, response rate, and proportion of adequately iodized salt at the household level. Studies that fulfill the inclusion criteria were screened and extracted by AAA, DBK, MYB, CTL, MD, MAA, & YMA using the pre-defined data extraction format. Then, the two authors (AAA, DBK) done quality assessment independently for the included studies using the Newcastle-Ottawa Quality assessment scale adapted for cross-sectional studies. The quality assessment scale includes representativeness of the sample, sample size satisfactoriness, non-response rate, and validity of measurement tool, comparability of subjects in different outcome groups, outcome assessment, and statistical test [8]. The 2 reviewers each (AAA and DBK) scored the included articles based on the above-mentioned quality assessment criteria. The combined quality assessment score for each study ranges from 0–10. The two researchers who extracted the data were discussed to solve any disagreements on data extractions under the mediator of the third author (YMA). Besides, the Microsoft Word PRISMA 2009 checklist was used to compile the report [9] (S1 File).

Outcome measurement

Adequately iodized salt at household level: If a household salt is fortified with the iodine content of ≥15 parts per million (ppm).

Statistical analysis

The data were extracted in excel and exported into Stata version 14 for analysis. The pooled estimate was computed using the “metaprop” command [10]. The original articles were described using forest plots and tables. There was statistically significant heterogeneity among studies. Therefore, we used a random-effect model to pool the proportion of adequately iodized salt at the household level. The pooled proportion with a 95% confidence interval was reported. Sub-group analysis was done by geographic location where the study was done, residence, year of publication, and sample size. Sensitivity analysis was done to check the influence of small studies on the pooled prevalence [11].

Heterogeneity test and publication bias

The presence of statistical heterogeneity within the included studies was evaluated using the I-squared statistic. The heterogeneity was classified as low, medium, and high when the value of I-squared was around 25%, 50%, and 75%, respectively [12]. We used Egger’s regression test to identify evidence of publication bias. Statistically significant publication bias was declared at a p-value of less than 0.05. The trim and fill analysis was done to quantify the effect sizes of missed studies [13].

Results

Search results

A total of 195 studies were identified by the electronic search in PubMed, Google Scholar, and Science direct. Of which, 5 articles were excluded due to duplication, 161 were excluded based on the exclusion criteria, 1 study was excluded since they did not report the outcome of interest [14]. Finally, 28 cross-sectional studies were found to be eligible and included in the current systematic review and meta-analysis (Fig 1).

Fig 1. PRISMA flow chart which shows the selection of included studies.

Fig 1

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Characteristics of reviewed studies

As shown in Table 1, a total of 28 studies (with 15561 households) met the inclusion criteria. Six regions and 2 city administrations were represented by this systematic review and meta-analysis. These are, 9 were Amhara region (n = 9) [6, 15–22], Oromia region(n = 8) [23–30], SNNPR (n = 4) [31–34], Tigray region (n = 2) [35, 36], Dire Dawa (n = 2) [37, 38], Addis Ababa (n = 2) [7, 39], and Benishangul Gumuz (n = 1) [40]. The smallest sample size (269) was reported from a study at the Sidama zone in SNNPR and the highest (1194) was from a study at the Dera district in the Amhara region. The quality score ranges from 7–10 with a quality score of good and very good. The proportion of adequately iodized salt at the household level as reported from the primary studies ranged from 4.6% at Dega Damot Districts of Amhara region [6] to 95.5% at Kolfie Keranio sub-city of Addis Ababa (7) (Table 1).

Table 1. Summary of the included studies which were done on the proportion of adequately iodized salt at HH level in Ethiopia, 2013–2020 (n = 28).

S.No. Authors Year of Publication Region Study Area Study Setting Sample size Response Rate (%) NOQS Proportion HHs using AIS (%)
1 Mesele et al. [16] 2014 Amhara Lay Armachiho Both 694 99.4 10 29.7
2 Mekonnen et al. [19] 2018 Amhara Dessie & Combolcha Urban 500 95.4 10 68.8
3 Ajema et al. [31] 2020 SNNPR  Arba Minch Urban 875 100.0 10 58.20
4 Abebe et al. [17] 2017 Amhara Dabat Both 705 98.7 10 33.20
5 Anteneh et al. [18] 2017 Amhara Dera Both 1194 96.2 10 57.2
6 Desta et al. [35] 2019 Tigray Ahferom Both 292 91.8 8 17.5
7 Gebriel et al. [40] 2014 Benishangul Gumuz Assosa Urban 395 100.0 10 26.1
8 Wondimagegn et al. [33] 2018 SNNPR Wolaita Sodo Both 440 99.8 10 36.7
9 Tariku et al. [20] 2019 Amhara Mecha Both 700 98.0 10 63.3
10 Gebremariam et al. [15] 2013 Amhara Gondar Urban 810 95.5 10 28.9
11 Hailu et al. [25] 2016 Oromia Robe Both 393 93.1 10 29.0
12 Gidey et al. [36] 2015 Tigray Laelay Maychew Rural 600 98.4 9 33.0
13 Yaye et al. [38] 2016 Dire Dawa Dire Dawa Urban 694 100 10 7.5
14 Hawas et al. [23] 2016 Oromia Assela Urban 513 96.4 10 62.9
15 Ayigegn et al. [7] 2020 Addis Ababa Kolfie Keranio Urban 541 95.5 10 95.5
16 Yazew [28] 2020 Oromia Horro Both 390 100 8 23.6
17 Meselech et al. [24] 2016 Oromia  Lalo Assabi Both 768 95.0 10 8.7
18 Hiso et al. [29] 2019 Oromia Duguda Rural 402 100 10 30.7
19 Woyraw et al. [22] 2018 Amhara Jabitehinan Both 549 98.0 9 48.3
20 Aredo et al. [27] 2020 Oromia Hetosa Both 596 98.8 8 61.1
21 Tigabu et al. [21] 2017 Amhara Gasgibla Both 443 97.6 10 17.2
22 Asfaw et al. [32] 2020 SNNPR Dewaro Zone Both 230 NR 7 19.1
23 Fereja et al. [26] 2018 Oromia Ada Both 351 98.3 10 39.3
24 Afework et al. [6] 2019 Amhara Dega Damot Both 802 100.0 10 4.6
25 Ftwi et al. [37] 2018 Dire Dawa Dire Dawa Urban 402 99.5 10 49.0
26 Belay 2020 Addis Ababa Kolfie Keranio Urban 417 98.5 10 63.8
27 Stoecker et al. [34] 2020 SNNPR Sidama Zone Both 269 NR 7 21.0
28 Tololu et al. 2016 Oromia Goba Town Urban 596 99.7 9 30.0
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NOQS: Newcastle Ottawa Quality Score; HH: Household; AIS: Adequately Iodized Salt.

Pooled proportion of adequately iodized salt

The pooled proportion of adequately iodized salt at the household level was 37% (95% CI: 28, 46%; I2 = 99.28%, p<0.001) in Ethiopia (Fig 2).

Fig 2. Forest plot of the 28 included studies which assessed the proportion of adequately iodized salt at HHs level in Ethiopia, 2013–2020.

Fig 2

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The subgroup analyses of 28 studies by residence revealed that the pooled proportion of adequately iodized salt at a household level among rural and urban residents was 32% (95% CI: 29, 35%) and 48% (95% CI: 31, 66%), respectively. Based on 28 included studies, the subgroup analysis of adequately iodized salt proportion at the household level by regions showed that the highest proportion was found in Addis Ababa (81%; 95%CI: 78, 83%) and the lowest was found in Dire Dawa (20%; 95%CI: 17, 22%). Also, the subgroup analysis of adequately iodized salt availability at the household level was done by the year of publication. The finding revealed that the proportion of adequately iodized salt at the household level was significantly increased during 2017–2020 (42%; 95% CI: 30, 53%) as compared with 2013–2016 (27%; 95% CI: 17, 39%) (Table 2).

Table 2. Subgroup analysis of the pooled proportion of adequately iodized salt at the HH level in Ethiopia by region, residence, & year of publication, 2013–2020.

Variables Subgroup No of included Studies Sample size Estimated proportion of AIS at HH level % (95% CI)
Region Amhara 9 6, 397 37 (23, 53)
Oromia 8 4, 009 35 (21, 50)
SNNPR 4 1, 814 33 (16, 53)
Tigray 2 892 28 (25, 31)
Addis Ababa 2 958 81 (78, 83)
Dire Dawa 2 1, 096 20 (17, 22)
Benishangul Gumuz 1 395 26 (22, 31)
Residence Urban 10 5, 743 48 (31, 66)
Both 16 8, 816 30 (21, 41)
Rural 2 1, 002 32 (29,35)
Year of Publication 2013–2016 9 4, 867 27 (17, 39)
2017–2020 19 10, 694 42 (30, 53)
Total 38 15, 561 37 (28, 46)
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Meta-regression

We run a random effect meta-regression by year of publication, region, residence sample size, and quality score to detect the source of heterogeneity. The finding evidenced that there is a statistically significant variation of the proportion of adequately iodized salt at HH by year of publication and residence across the pooled studies (p <0.05). The proportion of between-study variation explained by year of publication, region, residence, sample size, and quality score was 29.23% (Table 3).

Table 3. Meta-regression of the proportion of AIS by year of publication, region, residence, sample size, & quality score to detect the source of heterogeneity in Ethiopia, 2013–2020 (n = 28).

Variable Coefficient p-value 95% Conf. Interval
Year of publication 5.298441 0.012* 1.303038, 9.293845
Region -2.753277 0.235 -7.433168, 1.926615
Residence 8.815902 0.039* . .4790526, 17.15275
Sample size .0108135 0.581 -.0291769, .0508039
Quality Score 3.172159 0.546 -7.546717, 13.89104
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*Statistically significant variation.

Publication bias and sensitivity analysis

Funnel plot and Egger regression test methods were used to check publication bias. The finding evidenced asymmetrical funnel plot and statistically significant publication bias (p<0.05). The trim and fill analysis was done to quantify the effect sizes of missed studies. The finding showed that 10 studies with negative findings were missed from publishing. Besides, the sensitivity analysis finding showed that the individual studies did not have a significant impact on the overall pooled prevalence of adequately iodized salt at the household level.

Discussion

This systematic review and meta-analysis finding showed that the pooled estimate of adequately iodized salt at the household level in Ethiopia was 37% (95% CI: 28, 46%; I2 = 99.28%, p<0.001). The pooled estimate was varying by region, year of publication, and residence.

In Ethiopia, the pooled estimate of adequately iodized salt at the household level is low as compared to the world health organization’s (WHO) recommendation. According to WHO recommendation, the proportion of households with adequately iodized salt should be more than 90% to prevent iodine deficiency disorders among the population [2]. This implies that the population in Ethiopia was exposed to iodine deficiency disorders.

Based on the geographic location where the studies conducted, the highest pooled estimate was found in Addis Ababa (81%; 95%CI: 78, 83%), and the lowest prevalence found in Dire Dawa (20%; 95%CI: 17, 22). This variation might be due to weather variation across the regions, which affects the level of iodine content [34].

The subgroup analysis of adequately iodized salt by year of publication showed that the proportion of adequately iodized salt at the household level was significantly increased during 2017–2020 (42%; 95% CI: 30, 53%) as compared with 2013–2016 (27%; 95% CI: 17, 39%). This finding is in line with the finding of a study conducted based on 10 national coverage surveys in 2016 [41]. These substantial increments might be due to the government and different stakeholder’s efforts in enforcing USI laws and awareness creation on proper handling of iodized salt at the wholesaler, distributor, and household level.

The subgroup analysis of studies by residence revealed that the pooled prevalence of adequately iodized salt at the household level was higher among urban residents 48% (95% CI: 31, 66) as compared with the rural residents (32% (95% CI: 29, 35). This finding is also in line with the findings of a study conducted based on 10 national coverage surveys in 2016 [41]. Increased access to media and a high educational level in the urban area might be the possible explanations for this observed variation.

Limitation of the study

The findings of this meta-analysis should be interpreted considering the following limitations. The first limitation is that this meta-analysis did not find a study from the two regional states of Ethiopia (Gambella and Afar) which limits the generalizability of the finding at the national level. Second, heterogeneity among the included studies was high (I2 statistic = 99.28%, p<0.001). Third, there is a statistically significant publication bias (p>0.05). Hence, the random effect model was used to adjust the heterogeneity among the included studies. Also, meta-regression was done to identify the source of heterogeneity. The finding evidenced that year of publication and residence were the statistically significant variables introducing such a high variation among the included studies. Furthermore, trim and fill analysis was done to treat publication bias. The analysis indicated as 10 studies were missed.

Conclusions

In conclusion, in Ethiopia, the pooled proportion of adequately iodized salt at the household level was very low as compared to the world health organization recommendation. This indicates that the population in Ethiopia was exposed to iodine deficiency disorders. Thus, the Federal Ministry of Health of Ethiopia and different stakeholders should give more attention to improve the proportion of adequately iodized salt at the household level.

Supporting information

S1 File. PRISMA flow 2009 checklist of the study.

(DOCX)

Click here for additional data file. (30KB, docx)
S2 File. Dataset.

(DTA)

Click here for additional data file. (11.6KB, dta)

Acknowledgments

We would like to acknowledge the authors of original articles in which without their work this systematic review and meta-analysis could not be conducted. At last but not least, we would like to acknowledge Mr. Fasil Wagnew, a Lecturer at Debre Markos University for his thorough copy edit of the manuscript for language usage, spelling, and grammar.

Abbreviations

AIS

Adequately Iodized Salt

CI

Confidence Interval

HH

Household

ICCIDD

International Council for Control of Iodine Deficiency Disorders

IDD

Iodine Deficiency Disorders

NOQS

Newcastle Ottawa Quality Score

PPM

Parts Per Million

SNNPR

Southern Nations Nationalities and Peoples Region

USI

Universal Salt Iodization

WHO

World Health Organization

Data Availability

All relevant data are within the manuscript and its Supporting Information files.

Funding Statement

The authors received no specific funding for this work.

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Decision Letter 0

Shaun Wen Huey Lee

7 Dec 2020

PONE-D-20-26914

Availability of adequately iodized salt at household level in Ethiopia: a systematic review and meta-analysis

PLOS ONE

Dear Dr. Alamneh,

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.

Please submit your revised manuscript by Jan 21 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

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We look forward to receiving your revised manuscript.

Kind regards,

Shaun Wen Huey Lee, Ph.D.

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

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2. Please provide your rationale for restricting search timeline to 2013 onward? Why have earlier publications been excluded?

3. Please use standard statistical reporting of p values. For example, please delete p=0.000 and replace with p <0.001.

4.We suggest you thoroughly copyedit your manuscript for language usage, spelling, and grammar. If you do not know anyone who can help you do this, you may wish to consider employing a professional scientific editing service.  

Whilst you may use any professional scientific editing service of your choice, PLOS has partnered with both American Journal Experts (AJE) and Editage to provide discounted services to PLOS authors. Both organizations have experience helping authors meet PLOS guidelines and can provide language editing, translation, manuscript formatting, and figure formatting to ensure your manuscript meets our submission guidelines. To take advantage of our partnership with AJE, visit the AJE website (http://learn.aje.com/plos/) for a 15% discount off AJE services. To take advantage of our partnership with Editage, visit the Editage website (www.editage.com) and enter referral code PLOSEDIT for a 15% discount off Editage services.  If the PLOS editorial team finds any language issues in text that either AJE or Editage has edited, the service provider will re-edit the text for free.

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Additional Editor Comments (if provided):

The authors have written a well executed study and was in line with best practice. However, as highlighted by one of the reviewer, the authors ought to seek and use more inclusive languages in their manuscript as per PLOS guidelines.

[Note: HTML markup is below. Please do not edit.]

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: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

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: This paper is, for the most part, well written, straightforward, and easy to follow. Methods are appropriate and described adequately, and the statistical tests performed seem appropriate. However, it would be beneficial to read carefully through the manuscript to make sure everything is consistent and without typos. The topic is of importance.

Reviewer #2: I would recommend to edit and reformulate the background. The use if terms such as “mental retardation” and “fertility failure” are outdated and might even be considered offensive by vulnerable populations. I would recommend to substitue them with “cognitive impairment” and simply “infertility”, respectively.

Besides these remarks, I believe the data analysis can be of great relevance for the large scale nutritional interventions.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: Yes: Heber Gomez-Malave

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2021 Feb 16;16(2):e0247106. doi: 10.1371/journal.pone.0247106.r002

Author response to Decision Letter 0

16 Jan 2021

Response to Reviewers

Response to the Academic Editor

Dear Academic Editor,

Thank you for your invaluable comments and suggestions. We have addressed the points you raised as follows:

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

Response: Thank you! We have prepared the manuscript as per PLOS ONE guideline.

2. Please provide your rationale for restricting search timeline to 2013 onward? Why have earlier publications been excluded?

Response: Dear academic editor, thank you for your concern. The rationale for restricting a search timeline to 2013 onward is to generate more recent information that will be useful for decision making (Check on Method section, page 5, lines 104 & 105).

3. Please use standard statistical reporting of p values. For example, please delete p=0.000 and replace it with p <0.001.

Response: Thank you! We replaced it with p <0.001 (Check on page 10, lines 183; on page 13, line 221, and on page 14, line 250).

4. We suggest you thoroughly copyedit your manuscript for language usage, spelling, and grammar. If you do not know anyone who can help you do this, you may wish to consider employing a professional scientific editing service.

Response: The manuscript was thoroughly copy edited for language usage, spelling, and grammar by our colleague Mr. Fasil Wagnew who is a Lecturer at Debre Markos University (Check on “Acknowledgements Section” page 17, lines 296-298; and see the “Revised Manuscript with Track Changes”).

Response to Reviewer #1

Reviewer #1: This paper is, for the most part, well written, straightforward, and easy to follow. Methods are appropriate and described adequately, and the statistical tests performed seem appropriate. However, it would be beneficial to read carefully through the manuscript to make sure everything is consistent and without typos. The topic is of importance.

Response: Dear Reviewer, thank you for your suggestion to read the manuscript carefully in order to make sure everything is consistent and without typos. Thus, we have read and revise the manuscript (Check on the “Revised Manuscript with Track Changes”.

Response to Reviewer #2

Reviewer #2: I would recommend you to edit and reformulate the background. The use of terms such as “mental retardation” and “fertility failure” are outdated and might even be considered offensive by vulnerable populations. I would recommend you to substitute them with “cognitive impairment” and simply “infertility”, respectively. Besides these remarks, I believe the data analysis can be of great relevance for the large-scale nutritional interventions.

Response: Dear reviewer, thank you for your suggestion! We have edited those terms as per your suggestion (Check on page 3, line 64).

.

Attachment

Submitted filename: Response to Reviewers.docx

Click here for additional data file. (22.3KB, docx)

Decision Letter 1

Shaun Wen Huey Lee

2 Feb 2021

Availability of adequately iodized salt at the household level in Ethiopia: a systematic review and meta-analysis

PONE-D-20-26914R1

Dear Dr. Alamneh,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Shaun Wen Huey Lee, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

2. 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

**********

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

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. 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: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. 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: The author has thoroughly addressed all the comments given and thus I suggest the article be accepted for publication.

Reviewer #2: Thank you for carefully addressing the suggested changes. I believe your review will be of great value for public policies and health interventions.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Mario Sibamenya Venance

Reviewer #2: Yes: Heber Gómez-Malavé

Acceptance letter

Shaun Wen Huey Lee

4 Feb 2021

PONE-D-20-26914R1

Availability of adequately iodized salt at the household level in Ethiopia: a systematic review and meta-analysis

Dear Dr. Alamneh:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Shaun Wen Huey Lee

Academic Editor

PLOS ONE

Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 File. PRISMA flow 2009 checklist of the study.

    (DOCX)

    Click here for additional data file. (30KB, docx)
    S2 File. Dataset.

    (DTA)

    Click here for additional data file. (11.6KB, dta)
    Attachment

    Submitted filename: Response to Reviewers.docx

    Click here for additional data file. (22.3KB, docx)

    Data Availability Statement

    All relevant data are within the manuscript and its Supporting Information files.

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