Extraction of DNA and single-nucleotide polymorphism (SNP) genotyping DNA was extracted from 2556 individual participant samples and genotyping of 51 CHD-specific SNPs identified in Coronary ARtery DIsease Genome wide Replication and Meta-analysis (CARDIoGRAM PlusC4D) was completed, according to specification, by a company with specialised services for extraction of DNA and genotyping.