What is polygenic risk score?

Polygenic risk scores are becoming increasingly popular in the field of genomic medicine, evolving from applications in research studies to providing vital clinical genetic information in primary healthcare settings that will reduce the impact of common cancers on the general population.  

What is genetic testing? 

Every cell in the body contains a copy of the genetic code/DNA that makes us who we are and tells our body how to function. When cells replicate, the genes/genetic code is copied, and sometimes errors can occur in this process that the body is unable to correct. Genetic testing looks for changes in genes which indicate an increased risk of getting a disease. 

What is polygenic risk score? 

A polygenic risk score (PRS) is a quantitative tool that is used to predict an individual’s genetic predisposition of developing a disease over the next ten years. It summarises information over thousands of genetic variants (also called single nucleotide polymorphisms “SNPs”) in the human genome that either increases or decreases the risk of disease. 

What is the role of PRS in genetic testing? 

Genetic testing commonly analyses only single, or strong genes to identify faults. Whereas Polygenic risk score analyses thousands of weak genes to identify genetic changes or patterns. This information is then collected into a single score which shows an individuals’ risk of developing the cancer tested for over the next years.  

By combining the results from a strong gene panel and a weak gene panel, we can provide a more holistic and accurate way of quantifying the cumulative effect of multiple small genetic influences on the chance of developing a particular type of cancer.  

How is a person’s polygenic risk score calculated?

Once an individual’s PRS has been calculated, it is then compared to the risk of someone of their age in the normal population which is reported as a ratio. If the ratio is above 1.00 then the individual tested is at higher risk than the normal population. If it is below 1.00 then it is considered lower risk.  

Of course, a person’s risk can also be influenced by a wide range of factors such as lifestyle and environmental circumstances. By combining the polygenic risk score with a person’s background (origin, age, and gender), a person’s risk of developing a disease can be more accurately calculated so that regular screening can be sought from an early age.  

Polygenic risk scores provide a far more comprehensive form of genetic testing. It means that every single person tested can find out their personal level of risk, regardless of their family history or lifestyle, because a wider gene panel is analysed. 

What about family history? 

People may have a genetic predisposition to cancer even if they do not have a family history of the disease. For example, a woman may develop hereditary breast cancer even if she has never had a female relative with the disease. 

For those with a family history of cancer, genetic testing usually only analyses the faulty genes, and 80% of the time, these are found to be normal – even for those who have cancer family history. However, thanks to polygenic risk scores, where a full gene panel is analysed and patterns are identified, it provides a much clearer picture of identifying those at risk of developing cancer.  

What polygenic risk score doesn’t tell you 

Polygenic risk scores are not diagnostic.  A high risk-score does not mean that a person will definitely develop a condition, and a lower risk score does not mean that they will not.  

The benefits of polygenic risk score in primary healthcare 

In primary healthcare, polygenic risk scores can be used to identify the personal risk of developing cancer over the next ten years, allowing individuals to take an active role in their healthcare through better lifestyle choices. Earlier detection may also increase the chance of a successful outcome when it is more treatable.  

Everything Genetic’s innovative new cancer testing service Antegenes, not only utilises polygenic risk scores, but it also provides comprehensive clinical recommendations on precision prevention and early detection for individuals and their healthcare providers. 

 If you would like to find out more information about the Antegenes service and how to offer it as a complementary value-added service in your clinic or pharmacy, arrange a consultation with your Everything Genetic Account Manager by calling +44 (0) 1270 623 179 or emailing partners@everythinggeneticltd.co.uk