DNA was extracted from blood specimens within 5 days of the draw using Gentra Puregene reagents and protocols (http://www1.qiagen.com). Extracted DNA was quantified using the Pico Green method (Molecular Probes/Invitrogen), and all DNA solutions were normalized to a common concentration for genotyping assays. Genotyping was carried out using the Illumina HumanCNV370-Duo DNA Analysis BeadChip. Genotype generation and quality control were performed by deCODE Genotyping Service (http://www.decode.com/).
