Are all recessive disease carrier tests equal?

In several articles of this blog, we have discussed topics concerning the types of genetic diseases, including recessive diseases and their consideration mostly as rare diseases. We have also discussed the criteria to be followed when designing a panel for carrier screening analysis, where it was emphasized that the criteria for inclusion of diseases in carrier test panels are not completely closed, leaving room for the interpretation of each laboratory as to which diseases are considered severe or which affected systems are relevant when establishing this severity or the precocity of the age of onset. All this causes the existence of different panels with the same purpose, to determine the carrier status of recessive diseases in people willing to start a reproductive project.

As to the question of whether the different panels available are equal, the answer depends on the point of view according to which equivalence is interpreted. From a more general point of view, understanding equivalence as “same purpose”, the answer is yes. The different recessive disease carrier tests performed by genetic laboratories have the same purpose: to determine the carrier status of the person tested for recessive diseases in order to compare the results with those of his or her reproductive partner, thus allowing preventive decisions to be made about the diseases tested prior to or during pregnancy.

From a more concrete point of view, regarding whether the panels are compatible with each other when it comes to compatibility of the results, the answer is less categorical, depending on the results obtained by each person. That is to say, if a person, let us suppose her name is Maria, takes a carrier test and is identified as a carrier of only one disease that is included in all the carrier test panels (such as Cystic Fibrosis) then theoretically Maria’s analysis would be compatible with all the carrier tests given that her reproductive partner will have been tested for the disease of interest, whatever his carrier test may be. However, compatibility must be made taking into account the results of both patients. If the diseases for which Maria’s partner, let’s assume her name is Juan, are not included in the test performed on Maria, then the two tests would be incompatible and to determine the reproductive risk of the diseases identified in Juan it would be necessary to perform a new test on Maria to determine if she is a carrier of those diseases.

Consequently, the compatibility between different carrier tests depends on the results obtained by each member of the couple, given that when analyzing different diseases, there is the possibility that the design of the carrier test performed includes the analysis of the genes of interest (as in the case of the test performed on Juan for his compatibility with María) or that in the design of the test it was determined that a certain disease did not meet the criteria recommended by scientific societies for the design of carrier screening test panels (as in the case of the test performed on María for her compatibility with Juan).

Therefore, it is important to take into account different criteria when choosing a carrier test, among which, in case a member of the couple has already undergone a test, it is important to assess the compatibility between different panels in order to reduce the chances of having to perform new tests to determine the risk of offspring affected by the diseases tested. If the purpose of the tests is taken into account, another important consideration is to ensure that the test chosen is aimed at reducing the risk of offspring affected by recessive diseases in order to avoid those tests which, although genetic, do not have this as their main purpose and, consequently, do not achieve this objective.