All samples in the Bergen discovery cohort were genotyped using Illumina's HumanHap550 genotyping BeadChip (version 3) which contains 561,466 single nucleotide polymorphisms (SNPs). All samples that had a call rate <98%, and all SNPs that had a call frequency <99% were deleted. This resulted in the elimination of 23,436 SNPs from further analysis (See Text S1 for more details). The ICGN subjects were genotyped using Sequenom's iPLEX SNP genotyping protocol developed for measurement with the MassARRAY mass spectrometer [28]. Genotyping in the NETT/NAS and BEOCOPD studies was performed using Sequenom iPLEX or Applied Biosystems TaqMan assays. Genotyping in the Norwegian ECA Birth cohort was done by TaqMan.
