GSTM1 and thrombotic thrombocytopenic purpura: The mean hemoglobin (Hb) at the time of TTP diagnosis was 7.6 g/dL (SD 2.1), mean platelet level was 25.8 × 103/microL (SD 26.3 × 103), and median LDH level was 1422 U/L (range: 545–10,977 U/L).