using an additive genetic model. An unadjusted analysis and a logistic regression model adjusted for age and pack-years of smoking were conducted; sex was not included as a covariate because all NAS subjects were male, and current smoking was not included because all NETT subjects were ex-smokers. The BEOCOPD family-based study in the validation stage was analyzed using PBAT version 3.6 [30]. COPD was defined by post-bronchodilator FEV1/FVC<0.7 and FEV1<80% predicted (GOLD stage 2 or greater). Because a broad range of FEV1 values were included in the BEOCOPD study, we also analyzed FEV1 as a quantitative outcome in that population. Analysis of post-bronchodilator values of FEV1 was adjusted for ever-smoking status, pack-years of smoking, age, sex, and height.
