GSTM1 and anemia (phenotype): Of 67,595 patients analysed, 94.9% (n = 64,153) exhibited no or mild anaemia (Hb ≥ 9 g/dl), 3.7% (n = 2478) displayed moderate anaemia (Hb 7–8 g/dl) and 1.4% (n = 964) presented with severe anaemia (Hb < 7 g/dl).