Did you know that your genetic risk for myocardial infarction may be higher than the risk caused by smoking or elevated blood pressure? Science is currently exploring how to include our genome in the risk assessment for various diseases and use it to support the prevention and earlier detection of diseases.

Chronic diseases, such as diabetes, cardiac diseases and cancers, have a huge impact on the health and welfare of Finns.

The traditional methods for risk assessment and the prevention of diseases are rather established and generally known by professionals and citizens alike. Now, modern technology and new scientific discoveries are making it possible to include an objective assessment of the genome, or the impact caused by your genes, as part of a more extensive whole.

So-called genomic analyses, which cover the entire human genome, have produced a vast amount of information about the areas of the genome affecting different chronic diseases as well as individual genes. In recent years, studies known as genome-wide association studies (GWAS) have been conducted on many common diseases and traits. The studies explore how the different areas of the genome are connected to the examined issue. Worldwide, over 10,000 statistically significant associations to different human characteristics have already been reported on; naturally, diseases only form a part of these traits.

In polygenic inheritance, the onset of an illness is affected by not only environmental factors (such as a person’s lifestyle), but also hundreds if not thousands areas or variants of the genome operating together and separately, by interacting with the environmental factors and independently. The inheritance of chronic diseases is an extremely complicated whole, and the research on the topic has only just made a good start.

Polygenic risk score, PRS, summarises the impact of the entire genome in one chapter

As researchers have gained access to large genome studies, including UK Biobank from Great Britain and FinnGen from Finland, the researcher community has recently come to realise that the information about the differences in the genome between individuals can also be used to describe the personal disease risk caused by genetic factors.

In practice, this is done in a way that the millions of different variants in our genetic makeup are used to create a single number – a polygenic risk score (PRS) – that summarises the person’s genetic risk for a given disease in a form that is easier to process and understand. Among other things, the PRS indicates whether a person’s risk for developing a disease is lower or higher than, or equal as, the average risk level in the population.

The results of the GWAS studies mentioned above are used in calculating the PRS score. PRS presents a person’s polygenic risk in a single score, which may be included in the person’s comprehensive risk assessment along with more traditional risk factors.

Of course, the score does not exist in a vacuum, but must be related to other risk factors and the overall health of the examined person. It may be that the person has some other risk factor that is so severe that the PRS is practically insignificant.

For instance, the person may have a mutation of a single susceptibility gene that considerably increases his or her risk, or engage in a lifestyle that conceals the effect of the PRS.

A risk factor may also be protective – for example, evidence has already shown that if a person keeps his or her body mass index under control, his or her risk for type 2 diabetes will remain low even with a PRS making the person significantly susceptible to the disease.

In some cases, the PRS provides more information about an individual’s personal risk compared to many of the traditional risk factors frequently asked about or examined in connection with a doctor’s appointment, for instance.

The analyses by the UK Biobank indicated that the PRS value provides more accurate information about the risk for coronary artery disease compared to separate assessment of hypertension, diabetes, smoking, body mass index and family history of the disease. Naturally, combining different types of information is most informative.

Genetic data is permanent

Genetic data does not change. A risk factor such as blood pressure or cholesterol measured when a person is, say, 20-years-old is rarely the same as when the same person is middle aged, and does therefore not remain equally informative. By contrast, a person’s polygenic risk score, or PRS, remains unchanged.

As knowledge of the usefulness of the PRS increases, we may have at our disposal the means to guide the prevention of some diseases already when a person is still young.

The PRS can be determined based on a device known as a gene chip, currently priced at a few dozen euros, meaning that the costs are not different from regular, currently used laboratory examinations. Other useful genetic data can also be added to the gene chips, including the effect of the genome on the suitability and effectiveness of medications. This allows supplementing the information about a person’s genome.

Gene chips are currently mainly used for research purposes and by some companies in genetics; they have not yet been widely accepted for clinical use with patients.

Usefulness of polygenic risk score must be investigated before introducing it to general use

It is important to properly examine what sort of benefits determining polygenic risk can bring before introducing it to health care.

The method of calculating PRS has not yet become quite established. There is also need for assessing suitability of the score for different population groups and diverse life situations.

There is already evidence that PRS works better with some diseases compared to others. Nevertheless, the most important thing is to subject polygenic risk score, PRS, to the same scientific assessment process as any other test used in medicine.

From a big picture perspective, we are not yet aware of whether PRS will actually be helpful in providing anticipatory information or just end up increasing worries and costs.

THL examines and develops opportunities for utilising genetic data in health care

The Finnish Institute for Health and Welfare (THL) is implementing the P5 and P6 studies, which investigate the functionality of the polygenic risk score, PRS, and the opportunities for introducing its use.

The P5 study provides participants with information about their genetic risk for developing coronary artery disease, type 2 diabetes and deep vein thrombosis.

The Genomics to Healthcare (P6) project develops an operating model based on genetics for the use of health care and creates diverse collaboration and business opportunities to the industry.

The opportunities for utilising genetic data in health care were presented at ”Genomics to Healthcare”, a side event to Finland’s Presidency of the Council of the EU, on Friday 13 September. You can watch the seminar presentations and videos on the seminar website.
Genomics to Healthcare website

Read more:

P6 – Genomics to healthcare

The P5 study – Gene and metabolome information for health support 

Writer:

Markus Perola
Research Professor
Genomics and Biobank, THL

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