Results yielding a P value threshold of < 5×10−7 at loci not previously described7 in the moderate-to-severe and severe COPD meta-analysis of COPDGene, ECLIPSE, NETT/NAS, and GenKOLS (Norway) were subsequently genotyped in 983 probands and 1876 siblings from the family-based International COPD Genetics Network study (ICGN)34. Association analysis in ICGN was performed using PBAT (v3•61), under an additive model, adjusting for age and pack-years of smoking. Results from the family-based ICGN study were combined with case-control results using a joint meta-analysis41 weighted by sample size, using the number of informative transmissions in ICGN and the effective number of cases in each cohort. A joint meta-analysis P-value of < 5×10−8 was considered significant.
