TABLE 3.
Indicators of relevant causes and risk factors of anemia to be considered for assessment in surveys, surveillance, or program monitoring.
| Causes and risk factors of anemia | Diagnostic test, biomarker, or characteristics to identify condition | Proposed cutoff values or defining characteristics | Feasibility of collection | Cost |
|---|---|---|---|---|
| Causes | ||||
| Iron deficiency | Ferritin | Infants and children < 5 years (< 12 μg/L); children, adolescents, and adults 5 years and older (< 15 μg/L); pregnant women (< 15 μg/L)67 | Often requires venous blood collection but a sandwich enzyme-linked immunosorbent assay technique enables the collection of pools of capillary blood; cold chain required | $-$$$ |
| C-reactive protein, alpha-1-acid glycoprotein | Inflammation defined as CRP > 5 mg/L or acid glycoprotein > 1 g/L | Biomarkers of inflammation are required for accurate interpretation of ferritin67 | ||
| Infections | Parasitic (malaria, soil-transmitted helminthiasis [STH], schistosomiasis [SCH]) | Usually defined by the presence of infectious organism | Malaria and hematuria can be measured in the field from capillary blood and urine, respectively73 | $-$$ |
| Viral (HIV/AIDS, hepatitis C, respiratory viruses including COVID-19) | Mapping of STH and SCH is based on stool (STH and SCH) and urine (SCH) specimens74 | |||
| Bacterial (tuberculosis, salmonella, H. pylori, others) | Polymerase chain reaction testing diagnostic capacity variable for other infections | |||
| Inherited red blood cell disorders | Abnormalities of hemoglobin synthesis (alpha or beta thalassemia) | Usually defined with molecular tests by genotyping DNA extracted from dried blood cards | May be collected using dried blood cards, so is not dependent on venous blood collection or cold chain | $-$$ |
| Abnormalities of hemoglobin structure (Hb S, C, and E) | Hemoglobin electrophoresis can also be used to detect Hb S, C, and thalassemia | |||
| Abnormalities of red cell enzymes (G6PD deficiency) | Genotyping or phenotyping tests can be used; rapid diagnostic test kits for qualitative phenotyping tests available (typically below 30–40% of normal activity)76 | |||
| RBC membrane disorders (hereditary spherocytosis, elliptocytosis) | RBC membrane disorders can be diagnosed by RBC cytology, flow cytometry, ektacytometry, electrophoresis of RBC membrane proteins, and genetics75 | |||
| Blood loss | Onset of menstruation/menopause Hormonal contraception use Heavy menstruation Uterine fibroids Pregnancy and/or delivery complications | Usually defined by participant recall to questionnaires that include information about these characteristics | Requires the knowledge of cultural norms around reproductive health and birth | $ |
| Deficiencies in other micronutrients | Vitamin A | Retinol < 0.7 μmol/L (although for women is still uncertain)68 | Requires venous blood collection and cold chain, although folate can also be determined using dried blood cards. Limited availability of laboratories with externally validated performance | $$-$$$ |
| Riboflavin | Erythrocyte glutathione reductase activity coefficient > 1.369 | |||
| Folate | Serum folate < 6.8 nmol/L (risk of megaloblastic anemia) or RBC folate < 748 nmol/L (risk of neural tube defects)a,70 | |||
| Vitamin B12 | < 150 pmol/L (risk of megaloblastic anemia)71 | |||
| Risk factors | ||||
| Demographic and physiological status | Age Pregnancy/lactation |
Usually defined by participant recall to questionnaires | Requires the knowledge of cultural norms | $ |
| Socioeconomic characteristics | Income Educational attainment (incl. maternal education) Food insecurity Inequity, women’s empowerment |
Usually defined by participant recall to questionnaires | Requires the knowledge of cultural norms | $ |
| Lack of micronutrients and diversity in diet | Recent intake of animal source foods Recent intake of iron inhibitors (phytates, tannins) Recent consumption of foods fortified with iron, folate, and/or vitamin A Supplementation with iron, folate, and/or vitamin A |
Usually defined by participant recall to questionnaires | Requires the knowledge of common dietary patterns among target population | $ |
| Family planning practices | Onset of childbearing, parity, birth spacing | Usually defined by participant recall to questionnaires | Requires the knowledge of cultural norms | $ |
| Health practices/health services | Antenatal care during previous pregnancy Emergency obstetric and neonatal care Modern contraceptives Malaria prevention practices, if applicable Deworming, if applicable |
Usually defined by participant recall to questionnaires | Requires the knowledge of cultural norms and offered healthcare services | $ |
| Water access, sanitation, and hygiene | WASH practices | Usually defined by participant recall to questionnaires | Requires the knowledge of local practices and programs | $ |
| Social support programs | Poverty alleviation Income support programs |
Defined at regional level or by participant recall to questionnaires | Requires the knowledge of local programs | $ |
Abbreviations: Hb, hemoglobin; RBC, red blood cell; SCH, schistosomiasis; STH, soil-transmitted helminthiasis; WASH, Water Access, Sanitation, and Hygiene.
a
The cutoff depends on the laboratory method.
Source: Adapted with permission from USAID Advancing Nutrition.16