Association results from each dataset, including the beta coefficient and standard error, were provided to the coordinating team. Meta-analysis was carried out using PLINK [29] to obtain overall summary odds ratios (ORs) and statistics. The R package rmeta [30] was used to verify results and create plots. There was no evidence of significant heterogeneity across datasets for these analyses (minimum heterogeneity p = 0.21 for dichotomous CPD, 0.07 for lung cancer, 0.24 for COPD; for categorical CPD a nominally significant p was seen only for category 3 and locus 1 (p = 0.007)). Because of varying study designs, ascertainment strategies, and representative SNPs, we nevertheless report results from random effects meta-analyses.
