Table 1 indicates that groups A, B, and C were similar with respect to demographics, anthropometrics, menstrual history, past medical history, a variety of sociodemographic characteristics, and specific physical examination findings (ie, pallor, xeropthalmia, and goiter). Most importantly, the prevalence of anemia is similar among groups. The fact that these groups are similar, with respect to known prognostic factors, lends strength to the validity of the study results. Notably absent from baseline measures are indicators of iron deficiency (eg, microcytosis, serum ferritin, and free erythrocyte protoporphyrin). The authors comment that in a population with such a high prevalence of anemia, it can be assumed that iron deficiency anemia is the root cause. However, if iron deficiency was not evenly distributed among the 3 groups, it may have confounded the study results.