Genetic testing: the "Angelina" effect

It was perhaps inevitable that Angelina Jolie’s decision to go public about her double mastectomy last year would lead to a sudden and dramatic increase in the number in women signing up for genetic testing to find out if they too had the BRCA gene that would put them at high risk of breast cancer.
     While reports from the West indicate that the “Angelina effect” has cooled considerably, the interest in genetic testing is higher than at any time in history. But what exactly is it and, more importantly, is it really needed?
    Genetic testing is a detailed analysis of the DNA, the molecular structure of the chromosomes that carries the genes responsible for all body's functions. The technology can detect gene alterations or mutations, which are associated with certain diseases or conditions in a person and his/her relatives. While disease-specific genetic tests offer invaluable information for the patient and the physician, genetic testing for healthy individuals – sometimes sold as direct-to-consumer tests and increasingly advertised on the Internet – have many limitations and pose serious bioethical issues for health authorities.
    In medical practice, genetic tests are requested for valid medical reasons such as to determine the possible genetic cause of a disease, predict possible future illness in a person with a family background of an inherited disorder, assess the risk of transmitting a genetic abnormality to children and predict the response to a given therapy.
    These tests might provide a positive (disease is present) or a negative result (absence of the gene mutation) and also give an inconclusive result (test is not interpretable). For some illnesses, a positive or negative outcome is straightforward and irrefutably confirms or rules out the genetic abnormality. However, for many other genetic tests, the positive result indicates that while the individual has a higher risk of developing the disease, it does not mean that he/she will eventually get it. Likewise, the negative test stresses a low risk for the disorder but does not rule out development of the disease later in life. And so, a positive result for the breast cancer genes referred as BRCA 1 and BRCA 2 does not illustrate anything other than a high risk. It does not mean that breast cancer will definitely occur. Similarly, a negative test does not imply that breast cancer will not occur. While the positive test imposes stricter screening or other preventive approaches (like in some cases preventive surgical removal of the breasts), all women – with or without test results – need to adhere to annual breast investigations for the prevention of this most common cancer.
    The potential consequences of genetic testing outcomes require qualified genetic counselling prior to and after the test from a geneticist specialist able to provide clear and unambiguous explanations pertaining to the rational, limitations and interpretation of the test.
    Without proper advice, the result can trigger important emotional issues, irrational behaviour (such as stopping screening when the result is negative) and/or social implications such as tense family relationships when a gene problem is diagnosed. In France, for example, generic testing is highly regulated. By law, qualified physicians can only prescribe genetic testing for a meaningful purpose, which can result in subsequent valuable therapy or conduct.
    In contrast with a well-defined genetic test, some online companies are marketing a broad range of genetic tests directly to end-users without the advice and counselling from medical professionals. Instead, the client gets a genetic predisposition email for dozens of diseases including heart disease, cancers (lung, breast, bladder, prostate), lupus, diabetes, Alzheimer’s migraine and so on. The genetic study is based on the analysis of Single Nucleotide Polymorphisms (SNP), which have been identified as DNA markers associated with diseases or conditions. For each pathology the report highlights the risk of the individual in comparison with that of people from a similar ethnic group. In the summary table, the illnesses are categorised with higher, similar and lower risks than in control populations. In short, the person is advised of several predispositions to a certain number of diseases and a lower risk for other ailments.
    What such tests do not give is a correct interpretation of such worrisome outcomes or their implications with regard to subsequent therapeutic and behavioral approaches. In most cases, the identified predisposition to a given illness offers no specific therapeutic option other than healthy lifestyle recommendations and screenings, which are beneficial for any individual.
    The advertised interventions such as diet programmes and so-called individually tailored food supplements (often sold by the same company) to prevent or limit the risk of the disorder are not backed up by reliable scientific evidence. In view of the poor preventive interest and potential psychological harm, the US and French health authorities consider such deceptive practices as "misleading and of little or no practical use”. France, though not the US, strictly prohibits such layman-oriented genetic testing.
    Although genetic testing for healthy individuals undoubtedly opens up a new era of predictive medicine, the desire to learn about one’s genetic predisposition still requires the guidance of highly specialised and ethical medical professionals.

Dr Gerard Lalande is managing director of CEO-HEALTH, which provides medical referrals for expatriates and customised executive medical check-ups in Thailand. He can be contacted at [email protected].