A decision tree may be useful for determining which biomarkers to include when planning assessments of particular populations and population subgroups (e.g., women of reproductive age, pregnant women, children, or adolescents) [Figure 1].

The algorithm proposed below requires classifying a region of interest (national or subnational) as having a high or medium/low infection burden (first level). This designation can be made based either on bioindicators of infection or on other available indicators (e.g., the proportion of households without improved water or sanitation, the prevalence of schistosomiasis or soil-transmitted helminths). In communities with a high infection burden, the following level is to determine if the communities are malaria-endemic regions or not, and malaria may be the highest priority for assessment when determining causes of anemia in these regions.

Following the first two levels of the algorithm, based on infection burden and malaria presence in the population, the following analysis is based on the prevalence of moderate or severe anemia (based on the most recent available data). Under each category, there are several indicators listed to be used in case there are limitations in resources and access to diagnostic laboratories.

Figure 1. Proposed algorithm for prioritizing biomarkers to measure when assessing anemia etiology at the population level ^a

^aPopulation groups to consider when applying this process include pregnant women, non-pregnant women of childbearing age, children, and adolescents. Reproductive indicators will vary by population group (e.g., use of hormonal contraception or heavy menses for women; low birthweight or maternal anemia for children). Gray boxes with biomarkers are numbered from high to low priority for assessment. ^b Moderate and severe anemia defined per WHO guidelines (https://www.who.int/vmnis/indicators/haemoglobin.pdf, accessed Aug 11, 2020). ^c Infections (other than malaria) that directly cause anemia (not indirectly via inflammation) include helminthiasis and schistosomiasis. ^d Inherited hemoglobin disorders (IHD) protective to P. falciparum malaria need special consideration in anemia etiology assessment. ^e Micronutrient deficiencies other than iron that lead to anemia include vitamin A, folate, and vitamin B₁₂.