Figure 2 illustrates that individuals with COPD had significantly higher levels of Mefox compared to their non-COPD counterparts (p = 0.00612). Participants were stratified into four groups based on quartiles of log10-transformed Mefox levels: Q1 (log10 Mefox < −0.06 nmol/L, n = 2405), Q2 (−0.06 nmol/L ≤ log10 Mefox < 0.15 nmol/L, n = 2366), Q3 (0.15 nmol/L ≤ log10 Mefox < 0.37 nmol/L, n = 2389), and Q4 (log10 Mefox ≥ 0.37 nmol/L Hb, n = 2365). More information can be found in Table 1. Here, GSTM1 is linked to chronic obstructive pulmonary disease.