GSTM1 and chronic obstructive pulmonary disease: However, GSTM1(−) was present in 56 (28%) COPD cases and 73 (36.5%) healthy individuals and no correlation was found between GSTM1(−) and mMRC ≥ 2 for COPD risk (OR = 0.86, 95% CI = 0.56–1.33, P = 0.52) (Table 4).