MMP: metalloproteinase; TIMP: tissue inhibitors of metalloproteinase; CST3: cystatin C; FEV₁: forced expiratory volume in 1 s; % pred: % predicted; FVC: forced vital capacity; D_LCO: diffusing capacity of the lung for carbon monoxide; V_A: alveolar volume. Coefficients of determination (r²) and p-values were calculated from regression analysis of each clinical outcome including age, sex, race, pack-years and mRNA expression as covariates. r² values are for the whole model, p-values are for the mRNA expression level. FEV₁ % pred and FEV₁/FVC % were measured post-bronchodilator. An ordinal logistic regression was performed for the semiquantitative emphysema scores. D_LCO/V_A % pred was log-transformed. Significant results after correction for multiple comparisons are shown in bold. The p-value threshold is 0.05/(9×4.45)=0.0012. Complete results are shown in online supplementary table S7.