GSTM1 and anemia (phenotype): Even within the present analysis we found wide inter-country variations, with pre-treatment prevalence of anaemia ranging from 2.3% (in Liberia where patients had lower parasitaemia [19]) to 80.1% in Zanzibar, [21], and mean pre-treatment Hb from 8.6 g/dl, Zanzibar [21] to 12.9 g/dl in Liberia [19].