AGER and chronic obstructive pulmonary disease: To confirm that these differences were not due to smoking status, we compared serum EN-RAGE and sRAGE levels in former and current smokers across the smoker, mild/moderate COPD and severe/very severe COPD groups and saw no differences in the levels of these analytes between these 2 groups (Figure 2C and D, p  = 0.52 for sRAGE, p  = 0.98 for EN-RAGE).