GSTM1 and chronic kidney disease: Mean Hb and Ht concentrations in patients with CKD were lower than in patients with preserved kidney function (11.5 ± 1.2 g/dL and 35.1 ± 3.5% vs. 12.2 ± 1.6 g/dL and 36.0 ± 4.3%, although the differences were not statistically significant at p = 0.07).