A single saliva sample can point to genealogical relationships, ancestry and certain inherited risks, but it cannot predict the future or make a diagnosis on its own. This is precisely the boundary that is often obscured by the popularity of genetic testing.
The service is gaining popularity. Between January and August 2025, genetic tests were ordered 11% more often than during the same period of the previous year, while traffic to the websites of specialised laboratories tripled between January and July. In September 2024 alone, Genotek performed 15,000 tests.
What a saliva sample reveals
DNA is extracted from cells in saliva, genetic variants are analysed, and the results are compared with data from scientific studies and reference populations. According to Genotek's director of science, Alexander Rakityko, genetics is developing rapidly and the result is not a final document.
According to a study published in 2024, 71% of people who took a commercial DNA test wanted to learn more about their ancestry, while 50.5% were interested in their genetic characteristics.
Relatives and ancestry
The test can identify people who share sections of DNA. A parent and child or siblings share, on average, about 50% of their genetic material, while the share among cousins is approximately 12.5%. With each successive generation, the shared fragments become shorter and more difficult to trace.
However, a familial match is possible only if the person in question or one of their close relatives has a profile in the same database. That is why the genetic result often needs to be supplemented with family names, dates, archives and other family documents.
A DNA test does not determine nationality directly. It compares the genome with samples from different populations, and the results may vary depending on the database of the particular company and the representation of individual groups within it.
Genetic risk does not mean disease
Genetic analysis indicates the likelihood of a particular scenario, but it does not say with certainty whether a person will become ill. In inherited diseases, the link between a specific genetic variant and the disease may be clear. In obesity, type 2 diabetes, high blood pressure, some thyroid diseases, osteoporosis and glaucoma, other factors also play a role.
“The test does not establish a causal relationship. The result is more of a signal that should be taken into account when developing an individual monitoring plan,” explains geneticist Alexander Reznik.Biologist Alexander Panchin gives the example of a risk that doubles. If the initial probability is 1%, the genetic factor may raise it to 2% – the relative increase is large, but the absolute risk remains low.
In genes such as BRCA1 and BRCA2, limited testing for several common mutations may miss a rare pathogenic variant. Therefore, a commercial test should not be regarded as a substitute for specialised medical testing.
What should not be expected
According to Alexander Reznik, there is insufficient evidence for specific diets or eating plans derived solely from a DNA test. Genetic data can also be used in pharmacogenetics, but any change in treatment or choice of medication should be discussed with a doctor.
When planning a family, tests can show whether a person is a healthy carrier of a variant associated with an inherited disease. If the same variant is also present in their partner, the risk to the child may be higher. However, the mere presence of a genetic predisposition is not a verdict, but information that requires careful interpretation.
Sources: style.rbc.ru