What are carrier screening tests?
Carrier screening tests are analyses designed to determine whether the person being tested is a carrier of a recessive disease. Since it is necessary for a person to receive an altered copy of the same gene with recessive inheritance from both parents to be affected by a recessive disease, the determination of the carrier status of the person being tested makes it possible to know his risk of transmitting a certain disease to his offspring, even if the person being tested does not show any symptoms of the disease, having inherited only an altered copy of the gene.
The aim of the analysis, therefore, is to determine the risk of having offspring affected by a recessive disease by comparing the results of both members of the reproductive couple. If both members of the reproductive couple are identified as carriers of the same disease, it is possible to take informed reproductive decisions that would not have been possible with routine medical testing.
What are ancestry/wellness tests?
Ancestry tests aim to determine the population origins of the person being tested. This information allows the person to discover the ancestral origins of his family beyond the memories provided by his known ancestors. In some cases, it even allows the identification of previously unknown relatives.
The scope of the analysis is to highlight the ethnic mixture of the persons being analyzed, allowing a more global view of their family history, as well as the origin of some of their physical traits.
In some cases, ancestry tests also include genetic analysis related to wellbeing, such as pharmacological compatibility tests or predisposition to certain diseases. Always keeping in mind that these are results in a predisposition environment, so a medical evaluation is required to assess whether the person tested will be at risk of suffering any symptoms of the diseases for which an increased risk in comparison to the general population has been identified.
This information allows the person who undergoes the analysis to evaluate other ways to improve their well-being based on the variations identified in their genes, always considering the need to discuss the results with a specialized physician and the importance of leading a healthy lifestyle regardless of the possible genetic predispositions identified.
What do both tests have in common?
Both tests are based on the massive sequencing analysis of regions of interest in our genome. The analysis of the sequencing results is performed by comparison with a worldwide consensus human reference genome obtained by analyzing the sequences of thousands of people to determine which sequences are common and which sequences are identified in a small percentage of the population. The variations of the analyzed genome with respect to the reference genome are those that will be relevant to the analysis and will be reported in the context of the aim of the analysis.
What is the difference between the two tests?
Although in both cases the focus of the analysis is on the variations in relation to the reference genome used, in the case of carrier screening tests the variations of interest are those that are identified in a small percentage of the population and are localized in genes that have been described in relation to diseases with recessive inheritance. In contrast, in the case of ancestry tests, the variations of interest are those that are observed more frequently in one population than in another. These variations can be located in any region of the genome and, depending on their frequency and quantity, allow the identification of the percentage of ancestry contribution of each ethnic group to the person being analyzed. The variations that determine predisposition to certain diseases or pharmacological compatibility are variations that have been identified in greater frequency in people who have experienced certain symptomatology or response to drugs with respect to people who have not shown symptoms or who have obtained a different response to drugs.
In addition to the technical differences, there are also clear differences in the purpose of the tests and their clinical applications. Carrier screening tests must be prescribed by a physician or genetic counselor with the aim to improve the reproductive health of patients, whereas ancestry/wellness tests do not require a physician’s prescription.