GSTM1 and anemia (phenotype): In multivariable analysis, the risk of being parasitaemic on day 3 increased with baseline parasitaemia (AOR = 1.16 (95 % CI: 1.08–1.25), for every 2-fold increase in parasite density, P <0.001), fever (AOR = 1.50 (95 % CI: 1.06–2.13), P = 0.022), severe anaemia (Hb < 7 g/dl) (AOR = 2.04 (95 % CI: 1.21–3.44), P = 0.008) and being from areas of low/moderate transmission (AOR = 2.71 (95 % CI: 1.38–5.36, P = 0.004 compared to high transmission areas); see Table 5.