A polygenic risk score is an expression of someone’s likelihood of having or developing a particular medical condition. The score is calculated by evaluating information about multiple genetic markers.
At the 2019 SXSW conference, the genetic testing firm 23andMe announced that it would provide genetics-based risk analysis for type 2 diabetes to millions of customers. The company correlates genetic information from individuals with health-related data; the resultant data supports the construction of statistical models that can predict the likelihood of various traits and conditions from an individual’s DNA.
To calculate a polygenic risk score, the company explores the entirety of an individual’s genetic makeup, known as the genome. In the case of type 2 diabetes, analysis includes genetic markers at 1,244 locations in the genome, each of which has some relevance to development of the disease. Individual data, in conjunction with data from the statistical model, yield the polygenic risk score that quantifies the odds for that particular individual.
According to the company’s news release, 20 percent of customers would be told that their risk is higher than average; those in the high-risk category would have their scores quantified, as in a one-in-three chance of developing the disease. Those customers would also be targeted with marketing for a health-monitoring app from Lark, a 23andMe partner.
Many health experts have reservations about the usefulness of polygenic risk scores. In the case of type 2 diabetes, for example, excessive body weight may be more highly predictive than a score calculated from genetic data, and health habits may have more influence on development of the disease than heritable risk does.