GSTM1 and malaria: Fig 2 illustrates the frequency distribution of subjects across the range of observed G6PD activity values. The mean value among those ≥5 U/g Hb was 11·04 U/g Hb and set as 100% of normal enzyme activity. The thresholds of 10%, 30%, 70%, and 80% are illustrated in Fig 2. The distribution of malaria-positive subjects by species of diagnosis, also in Fig 2, appeared independent of G6PD activity level.