Figure 5.

Biomarker distribution in nonsmokers, healthy smokers (HS), and smokers with increasing severity of chronic obstructive pulmonary disease (COPD), showing biomarker relationship to disease severity using (a) absolute biomarker values (weight/ml) and (b) values normalized for protein content (weight/pixel density unit [pdu]). Asthmatic nonsmokers are included as a chronic airway disease control. Only the P values of the primary comparison (see Statistical Analyses) between HS and subjects with stage 2 COPD. Lines represent the median values, boxes the standard deviation, and bars the range, excluding outliers. PSP94 = prostate secretory protein of 94 amino acids.