the genome in large numbers of individuals (hundreds to tens of thousands) with and without a particular common condition. These genotypes are then queried for associations between genome variants and disease status. The first major GWAS, published in 2005, revealed a previously unknown relationship between variations in the complement factor H gene and age-related macular degeneration.11 This publication heralded an avalanche of subsequent studies of common conditions – including such pediatric concerns as asthma, type 1 diabetes, inflammatory bowel disease, and autism.12 Gene chips can be configured for specific clinical diagnostic and prognostic purposes, and can inexpensively measure large numbers of point mutations in a sample. The chips’ accuracy depends on the specific platform, but is generally quite high, especially for single base pair changes measured in a DNA sample, where sensitivity and specificity can exceed 99%.
