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Dr. Joaquim de Sá

Medical Genetics Consultant


Unilabs Genetics Medical

Dr. Joaquim de Sá

Personalized preventive health care?

The possibilities of medical genetics

HPA Magazine 20

As we know, a good part of the medical progress of the last few decades revolves around early diagnosis, and we can even foresee a change in the paradigm from treatment to prevention. 
It is in this context that genetics has gained relevance by providing tests with effects in primary prevention as well as in pre-symptomatic diagnosis.
Synergistically, each of us pays more and more attention to the health of ourselves and those we love, with the promotion of healthier lifestyles already a constant in the public space. 



 

At present, this promotion takes place allied to the display of a personal well-being that is recurrently in the background of any advertisement, from food to detergents, from cars to banks, from TV to instagram.
Genetics has also established itself as a consumer product associated with health promotion, essentially through tests that promise to recommend the best nutritional plan or the most appropriate physical exercise, with attention to vitamins and micronutrients and metabolism, providing personalized responses to each interested party. 
However, these results still do not materialize Galen's personalized medicine dream with almost two thousand years, since, in the vast majority, inferences with clinical validity will be minimal or absent, given the relative risks being less than 2. 
When adding the risk of inadequate data protection of the test raw results (susceptible to a deep analysis in the future by artificial intelligence) my enthusiasm for these susceptibility studies does not allow me to recommend them even for recreational purposes. The other tests I wanted to talk about are very different, as they can be exceptionally relevant in promoting health, whether in the preconception or prenatal context or in a healthy adult.
It is estimated that there is a 2 to 3% risk of a child being born with a serious illness. 
The risk for severe recessive diseases is estimated to be less than 1% for the general population. 
However, if both members of the couple are carriers, the risk is 25% or, if the mother is a carrier of an X-linked recessive disease, the risk would be 50% for male children.
 

As carriers are almost always asymptomatic, none of us knows their carrier status for each of the more than a thousand diseases, although this information is relevant when considering a parental project. 
Although it has been possible for decades to search for a family disease in the fetus at the beginning of pregnancy, we were only able to do so when a relative with the disease was already known (often the couple's previous child).
However, it has now become feasible to identify couples with a significantly increased risk of severe recessive disease in their offspring, but with a negative family history, by joint analysis of all genes associated with autosomal recessive or X-linked diseases. 
Cystic fibrosis, spinal muscular atrophy or the fragile x syndrome are some of the most well-known pathologies. Couples at significantly increased risk are offered disease-specific molecular prenatal diagnosis or preimplantation genetic diagnosis. In the prenatal context, the non-invasive test in fetal DNA for frequent aneuploidies allows the exclusion of trisomy 21 with high sensitivity.
This test, very popular with several commercial names, as well as the carrier identification test, still very little known, already have published recommendations for use, such as the Practice Guidelines of the American College of Medical Genetics and Genomics dated 2021 and December 20221).
In healthy adults, finally, it is possible to carry out a pre-symptomatic test to assess the genes related to a hereditary oncological disease, thus allowing adequate medical surveillance and more management options (e.g. prophylactic mastectomy) for people in whom the pre-symptomatic diagnosis is established. These tests certainly have limitations, but I remember that at the HPA it is always possible to schedule interdisciplinary meetings so that together we can arrive at diagnoses that allow for the most appropriate counseling of the people who consult us, as well as to schedule medical genetics video consultations, which is a simple way to win distances and gain time, enabling adequate pre-test and post-test genetic counseling, with informed consent, always in accordance with the law.