Consistent with the SNP effects, clinically relevant anemia was not associated (p = 0.12) with ITPA activity while there was a strong effect of ITPA activity (P = 1.1x10-4) on the rate of early Hb decline ranging from 15% for 30% activity to 52.3% for full activity (Fig 2B). Here, GSTM1 is linked to anemia (phenotype).