BY SHREYA SHRIRAM | SQ ONLINE REPORTER | 2018-2019
A few decades ago, the idea that one could know their risk of developing a specific medical condition would have been considered far-fetched. However, recent advances in the fields of genetics and genomics have made several types of genetic testing available. These techniques have the ability to provide individuals with important, and perhaps life-changing, information about their futures and those of their children. Though these new technologies have aided people in many ways, allowing them to become more informed about their futures, they also come with many potential concerns.
Currently, some of the main types of genetic testing available include diagnostic testing, presymptomatic/predictive testing, and prenatal testing. (Note: this is far from an exhaustive list; there are several other types of genetic testing available which I will not go into detail about.) Diagnostic testing is a form of genetic testing which screens for a certain mutation in an individual’s DNA. Presence of this mutation is an almost definitive diagnosis of the disease. A somewhat similar (but distinct) type of testing is presymptomatic testing (or predictive testing). This tests the individual for a mutation which may put them at increased risk of a condition, but it is not a certain diagnosis. Finally, preimplantation genetic testing is most useful for couples who are known carriers for a genetic condition. All of these techniques have the potential to bring about great benefits to individuals but can also cause monumental harm if used blindly, making it important for them to be used with caution.
At this point, a common question arises: exactly what conditions can these tests screen for? In the case of diagnostic testing, it is most often used to detect diseases caused by chromosomal aberrations, such as Huntington’s disease (HD). HD is a dominantly inherited condition caused by the mutation of a gene on Chromosome 4, which results in a high number of repeats of the nucleotide sequence “CAG.” Normally, individuals have ≤ 35 repeats of this sequence, but HD patients have upwards of this number, with more repeats corresponding to earlier onset and more severe symptoms. Symptoms of HD include both physical and cognitive components, such as uncontrollable jerking, muscle problems, and impairment of voluntary movements as well as lack of focus and awareness. These symptoms lead to a progressive loss of physical and mental control that eventually results in death.
In the case of presymptomatic testing, the main purpose is to test for the risk of a future disease by looking for mutations associated with an increased risk for said disease. A key example is testing for the BRCA1/BRCA2 mutations. Presence of a mutation in either BRCA1 or BRCA2 increases a woman’s risk of developing breast cancer to ~70%, which is six times higher than that faced by women without the mutation; it also greatly increases their risk for ovarian cancer (a 17-44% risk, vs. a <2% risk for those without the mutation). The main difference between presymptomatic and diagnostic testing is that the former can only tell an individual that they are at an increased risk for a certain disease, while diagnostic testing can inform an individual with almost full certainty whether they will develop the disease later on in life.
Preimplantation diagnostic testing is used by couples who are trying to conceive, with one or both parents being carriers of or affected by a heritable chromosomal abnormality or single-gene condition. Embryos created via in vitro fertilization (IVF) are tested for the condition before implantation, and the healthy ones are transferred to the uterus to be implanted.
Though all of the mentioned types of genetic testing have several benefits for individuals, they can come with very negative consequences. In the case of diagnostic testing, and even presymptomatic testing, one’s life and life plans can be irreversibly changed. Knowing that they are at risk for developing a condition can cause serious mental and emotional strain on an individual. Katharine Moser discusses her tumultuous days following a positive test for HD, describing that she “often found herself unable to remember what normal had once been…She never, she said, regretted being tested. But at night, crying herself to sleep in the dark of her lavender bedroom, she would go over and over it. She was the same, but she was also different. And there was nothing she could do.” Many others suffer from similar situations following such devastating news of an impending genetic disease. This illustrates a key concern with genetic testing, which is the lasting psychological and emotional damage that it can inflict on those who get tested.
In the case of presymptomatic genetic testing, there arises the difficult situation in which individuals must weigh the pros and cons of undergoing preventative procedures. As discussed earlier, women with the BRCA1/BRCA2 mutation are at a greatly increased risk of developing breast and/or ovarian cancers. A preventative bilateral mastectomy has been shown to be an extremely strong protective measure, reducing an at-risk woman’s chances of developing breast cancer by 90-95%. However, presymptomatic testing does not say for sure whether a woman will develop cancer, only that she is at increased risk due to the presence of the mutation. This poses a vexing dilemma for many women in this situation: of course, the “safest” option would be to undergo a mastectomy. On the other hand, what if the procedure is not necessary, and the woman will never develop cancer? This results in a lot of unneeded expense and stress, not to mention the impact that such a surgery has on a woman’s body image and overall life.
Preimplantation diagnostic testing, though it can enable families to conceive healthy babies, comes with its own plethora of negatives, with the primary one being sex selection of babies. Many couples use this testing not to create a healthy baby, but to choose their child’s gender. This raises serious ethical concerns, as it can lead to harmful trends in populations, particularly in societies which have a skewed preference for male children. It teeters dangerously close to, if not already within, the territory of eugenics, which is defined as “the science of improving a population by controlled breeding to increase the occurrence of desirable heritable characteristics.” Overall, with the availability of several different types of genetic testing today, there is room for great progress and improvisation in healthcare. However, there is equal room for abuse of these innovations and for straying into dangerous and unethical territories. A much-needed starting point towards preventing this is the implementation of more stringent guidelines regarding these methods of testing and their uses — a precaution that will hopefully enable the risks of these procedures to be thoroughly weighed against their benefits and reduce the chances of potentially harmful results, both on the individual level and for society as a whole.