Correlations between lung function parameters and CLCA1-expressing epithelia. (A) Age and CLCA1 protein expression. (B) Brinkman index and CLCA1. (C) %predicted VC and CLCA1. (D) FEV1 and CLCA1. (E) FEV1/FVC and CLCA1. (F) %predicted FEV1 and CLCA1. (G) PaO2 and CLCA1. (H) PaCO2 and CLCA1. Results are for non-smokers (circles, n = 7), smokers without COPD (triangles, n = 7), and COPD patients (squares, n = 6). Associations between variables were assessed by Pearson correlation coefficients (* p ≤ 0.05).