The Limits of Genetic Testing

The public perception of genetics has been skewed and twisted by the ignorant media portrayal of what genetics, especially what clinical genetics, can presently do. What many fail to realize is that molecular genetics can be useful only in diagnosis at the level of application we have mastered. Genetic therapy for most diseases is still under investigation and will not be available as a practical option until further knowledge is collected and technological advancements have been made.

Over the summer, I worked in the Molecular Pathology Lab of a hospital. I was directly involved in the genetic testing for a patient diagnosed with breast cancer; it was my duty to detect and to confirm what had caused her body to succumb to the hereditary curse of breast cancer. She had already fallen victim to the mutation and therefore, could not be "cured" through finding what mutation existed in her genome . Although through genetic counseling, she knew what limited comfort the knowledge she would gain could bring her, she proceeded to have the testing done.

Cancer testing does not equal cancer therapy in terms of genetics. Knowing what sequence has been altered does not allow for the clinical geneticists to "fix" it back to the cancer-free sequence. It is one thing to find the mutation. It is a completely different issue with a whole new set of techniques and knowledge to change the DNA sequence of a living, complex organism. This is where public perception deviates from the current state of clinical genetics.

Of course diagnosis has its virtues. An analogy that may be helpful here is that of a Russian Roulette. Genetic testing can tell you how many bullets you have in your gun and tell you what risks are involved. What it cannot do is remove those bullets or stop the game. To make things even worse, the negative result does not mean that you are risk-free.

The negative results may often be worse than positive results for the patients. Many people come to get tested in order to find some peace through knowledge and confrontation with the demon encoded in their genome. The clinical geneticist may run the standard tests for frequent mutations and come back with all negatives. This only means that the patient does not have the standard mutations. It could very well be that the patient has an unreported, undiscovered mutation that could be a point mutation in a gene that has 4000 base pairs. The patient can pay over $1000 for the complete screening of one potential disease-related gene. But once again, there is nothing that guarantees that the gene is not associated with another gene that may contain the mutation. The patient could very well have a normal sequence in the gene directly associated with the disease and there could be another associated gene that has the disease-inducing mutation in its sequence. The entire process becomes a complex web of possibilities for further testing. A positive result for a mutation may end the search for the cause of the hereditary struggle, but testing may very well open doors to further mysteries by coming back as negative results.

What can happen after the patient is given a positive result? There are numerous preventative measures a patient can take once he/she is informed of her genetic time-bomb. Since most cancers, including breast cancer, follow a "two-hit model" where an in-born mutation only shows its effects once, the patient goes through an induction of a second mutation of the non-mutated allele. Therefore, by being more careful of avoiding carcinogens, the risk of developing cancer may be decreased. The relatives of the patients may be informed and they can be tested for the mutation as well, in order to start preventative measures.

Here lies another ethical issue intertwined with genetics : relatives. The patient may want to know about his/her mutation, but his/her sibling may not. It is understandable if a person refuses to find out about his/her mutational status; after all, there is no therapy involved in testing. Prevention can easily be done without concrete knowledge of having a genetic time-bomb within your system. If the patient happens to test positive for a prevalent mutation, should he/she tell his/her relatives? Whose information is it? The DNA is the patient's property, but the information may all be similar to that of the sibling's. But not knowing about the mutation, the sibling may not take proper preventative measures and induce cancer on him/herself. Does that make the patient who did not tell the sibling responsible for the potential death of the sibling? What if the sibling had refused to listen about the mutation? Does the refusal to acknowledge the information from the patient make the sibling responsible for his/her death?