S100A4 and chronic obstructive pulmonary disease: Multivariable linear regression found that serum S100A4 was inversely associated with FEV1% (β = −0.435, 95% CI: -1.962~-0.939), FEV1/FVC% (β = −0.212, 95% CI: -0.729~0.090), FEV1 (β = −0.434, 95% CI: -0.865~-0.046), and FVC (β = −0.405, 95% CI: -0.041~-0.018) in COPD patients (Table 2).