In addition, we tested for a potential interaction between low hepcidin and sex and observed a significant interaction in which the odds of low hepcidin being associated with severe anemia was limited to females (OR 4·85, 95%CI 1·79–13·09 in girls vs 1·44, 95%CI 0·71–2·92 in boys) with a Mantel Haenzel test for heterogeneity of p = 0·046. The gene discussed is HAMP; the disease is anemia (phenotype).