GSTM1 and diabetes mellitus: The results showed that mean_Hb and mean_HCT were protective factors for subgroups of age <59.3 years, age ≥59.3 years, female, male, CKD stage 3, with hypertension, with diabetes mellitus, and without diabetes mellitus (p<0.05) and were not statistically significant in the subgroups of CKD stage 4 and without hypertension.