GSTM1 and chronic obstructive pulmonary disease: Significant differences were observed in hemoglobin (Hb) levels, white blood cell (WBC) counts, ALB, TB, IB, BNP, C-reaction protein (CRP) levels, FEV1, vital capacity (VC), PaO2, PaCO2 levels and proportion of GOLD 1 + 2 between COPD-PH patients living at LA and HA (P < 0.05).