GSTP1 and chronic obstructive pulmonary disease: Since 4 studies had PHWE <0.05 (Zhang et al., 2003; Calikoglu et al., 2006; Korytina et al., 2009; An et al., 2019b), we conducted a subgroup analysis of 27 studies with PHWE≥0.05 and established that GSTP1 rs1695 [homozygote model (OR = 1.586, 95% CI = 1.210–2.080, PZ = 0.001) and recessive model (OR = 1.533, 95% CI = 1.273–1.846, PZ = 0.000)] was significantly associated with COPD risk, consistent with findings in the overall analysis, indicating that some studies with PHWE <0.05 did not affect the overall results, which were reliable.