GSTM1 and anemia (phenotype): Anemia prevalence was higher when using WHO-corrected Hb, 27%, and Silubonde’s criteria, 41% (Hb cut-off of 11.10, 12.73, 15.80 and 16.60 g/dl for altitudes of 130, 150, 3800 and 4300 meters, respectively), than using uncorrected Hb to define anemia (7.7%).