GSTM1 and anemia: However, when G6PD activity was adjusted by Hb concentration to produce the standard unit of the enzyme’s activity, no significant difference was observed between malaria cases with anaemia and those without anaemia (15.9 U/gHb [13.1–19.1] vs. 16.2 U/gHb [13.2–17.7], p = 0.712) (Table 2).