What are polygenic risk scores (PRS)?
Imagine knowing your genetic predisposition to developing diseases such as type 2 diabetes, cardiovascular disease or certain cancers, before a single symptom appears. That is exactly what polygenic risk scores (PRS) offer.
Unlike monogenic diseases —caused by a single gene mutation—, most common diseases are polygenic: they are influenced by hundreds or thousands of genetic variants, each with a small effect. A PRS combines the effect of all those variants into a single figure estimating your relative risk compared with the rest of the population.
How is a PRS calculated?
The process starts from genome-wide association studies (GWAS), which analyse millions of genetic variants in thousands of people to identify which ones associate with a particular disease. From there:
- The relevant variants are selected — from a few dozen to millions of SNPs.
- Each variant is weighted according to the magnitude of its statistical effect.
- Effects are summed across your specific genome to obtain an overall score.
The result is compared with the population distribution: if your PRS sits at the 95th percentile, your genetic risk is higher than that of 95% of the reference population.
Which diseases do PRS cover?
The PRS with the strongest scientific evidence include:
- Coronary disease — people in the top percentile have up to 3 times higher risk.
- Type 2 diabetes — identifies high-risk individuals decades before onset.
- Breast cancer — complements BRCA1/BRCA2 testing, capturing additional polygenic risk.
- Colorectal cancer — useful for stratifying screening programmes.
- Alzheimer’s disease — beyond APOE, PRS adds relevant predictive information.
- Atrial fibrillation, obesity, asthma and many more.
PRS and preventive medicine
The true value of a PRS is not labelling anyone as a “future patient”, but empowering prevention. An elevated polygenic risk for cardiovascular disease can motivate lifestyle changes, closer laboratory follow-up or even early statin indication, all supported by recent clinical guidelines.
Limitations you should know
No genetic tool is perfect, and PRS are no exception:
- They are not deterministic — they indicate probability, not certainty. Environment and lifestyle modulate risk.
- Population bias — most GWAS have been conducted in European populations. Their predictive power may drop in other ethnicities, although this bias is being actively corrected.
- They need clinical context — a PRS must be interpreted together with family history, biomarkers and patient habits.
- They evolve — as more data accumulate, models improve and scores are recalculated.
How can I get my PRS?
At OmicaLabs we calculate polygenic risk scores from your personal genome data. Our GenePortal report includes validated PRS for the main common diseases, with clear clinical interpretation and personalised recommendations.
If you want to know your genetic risk map and make informed decisions about your health, see our personal genome service. Preventive genomics is no longer the future: it is the present.