Use in clinical context
Genome-wide association studies (GWAS) analyse genotype information from between 500,000 and one million variant sites (loci) throughout the genome from a large number of people with the trait (or condition) and people without the trait.
These studies can identify genetic variants associated with traits or conditions by comparing groups of affected and unaffected individuals. If a particular genetic variant is found more in affected individuals, it suggests that the variant is associated with the trait or condition.
An association does not usually mean that the genetic variant is causing the trait or condition, but it does indicate that the variant responsible may be found in that section of the genome. With additional work it can be possible to identify the variant responsible.
Examples of conditions where GWAS have identified genetic variants which have led, or look likely to lead, to targeted treatments include type 2 diabetes, rheumatoid arthritis and osteoporosis.