Limitations of Hb assessments and blood sampling have been associated with varied anemia prevalence estimates.48,49,50,51,52,53,54 In our data, capillary vs venous blood draw was not associated with assignment of the healthy status in the overall population, and among the healthy subpopulation, blood sampling was not associated with Hb, inflammation, or vitamin A concentrations (data not shown). This evidence concerns the gene GSTM1 and anemia.