Is genetic testing helpful in combating common severe diseases?
The widespread diseases prevalent in our society include cardiovascular disorders, cancer, bowel diseases, psychiatric pathology and metabolic conditions. A large number of heterogeneous genetic and environmental factors determine their onset and course. The advances in molecular genetics research accruing from the sequencing of the human genome are increasingly revealing correlations between these disorders and certain genetic variations.
But how useful are genetic analyses in clinical practice for establishing the probability of a disease?
The seven experts from various medical specialities and the field of bioinformatics were unanimous in their response to this question. In spite of the rapid pace of increase in the volume of available information on the involvement of a number of genetic variants in the risks of pathology, the medical value of these discoveries is still questionable. The main reasons for these doubts are considered to be that as a rule each of the genetic variants concerned has only a very slight effect on the risk of falling ill, that the overall risk of contracting a disease is determined by a number of variants simultaneously, and that the variants also influence each other. In addition, the genetic variants exhibit complex interactions with environmental factors. For this reason, all the contributors feel that there is little point, now or in the future, in the large-scale deployment of genetic testing for the prediction and early diagnosis of common severe diseases. This is so particularly because the identification of an increased risk would lead not to new options for treatment but merely to general recommendations for a healthy lifestyle, which are, however, already urged on the population independently of any increased risk.
Disorders are stated to have been successfully predicted so far solely in the comparatively rare cases where the relevant risk is determined by only one or a small number of genetic variants. These include, for example, three of the genetic variants involved in early-onset Alzheimer’s, mutations of the insulin receptor gene in diabetes or mutations in certain enzyme genes in myocardial infarction.
In the view of the experts, advances in the prediction of pathology can in addition be expected from epigenetic testing and the identification of new biomarkers relevant not only to the basic genetic endowment but also, and in particular, to the activity of the genes concerned.
The application of genetic information is also felt to be promising in pharmacogenetics, in which the effect of genetic variants on the action of medicinal products is analysed with the aim of adapting drug selection and dosage to the individual patient.
All the experts consider highly qualified medical advice consistent with the complexity involved in the use of genetic testing to be essential. This is not necessarily forthcoming with the genetic tests available online. However, even where genetic tests are conducted in the context of medical treatment, new challenges arise, as a result of which interdisciplinary collaboration between various specialities will be still more important in the future.
Issues addressed in the ensuing discussion included the extent to which genes could be regarded at all as causative factors in disease, the possible and desirable repercussions of increasing genetic knowledge on the shaping of our healthcare provision, and whether a fundamental review of the prevailing organ-based conception of illness is called for.