BTAF1 and chronic obstructive pulmonary disease: Case-control stratification identified three SNPs nominally associated with k in moderate-to-severe COPD (rs6481619 within SVIL β = 0.152, P = 0.013; BTAF1 β = 0.196, P = 0.046; rs7386139 within DEPTOR β = 0.159, P = 0.047).