We next sought to determine whether there was evidence for secondary associations at each described locus. We performed analyses conditioning on the top (lead) SNP at each genome-wide significant locus reported in this analysis, examining all SNPs present in 250kb flanking regions around the top signal. We found evidence suggestive of secondary associations (P < 5×10−4) in the analysis of moderate-to-severe COPD at 15q25 (conditioning on rs12914385) for a SNP in strong LD (r2=0•92 in EUR) with the previously reported rs13180 in IREB2 (rs12903295, intronic in IREB2, P = 9•9 × 10−5). Suggestive evidence of a secondary association was also found near the 14q32 (RIN3) locus conditioning on rs754388 (rs11849228, P = 1•3×10−4). In severe COPD, evidence supporting a secondary association was found at 15q25 in another intronic SNP in CHRNA3 (rs3743073, P=3•3×10−4).
