GSTM1 and anemia (phenotype): Overall, prevalence of anaemia (Hb<12g/dL) was 49.8% (95%CI 24.2–28.7), out of which 60% was moderate anaemia (Hb between 8.0–10.9g/dL), and 37% were with mild anaemia (Hb between 11.0–11.9g/dL for children aged 12 years and above, or 11.0–11.4g/dL for children below 12 years old, and 11.0–12.9g/dL for boys aged 15 years.