In comparing the shortlisted 46 candidate gene lists associated with distinguishing mild from moderate COPD classified by FEV1 (TPCH-FEV1) to the study where seven genes associated with distinguishing mild from moderate emphysema classified by KCO (TPCH-KCO) [13], only one gene, COL6A3 (collagen, type VI, alpha 3) was common to both phenotypes. Here, COL6A3 is linked to chronic obstructive pulmonary disease.