Personal DNA Testing
Personal DNA Testing
Neil deGrasse Tyson submits his spit for analysis in order to get a personal genetic profile that will predict his chances of contracting one of several serious diseases. But would you? Several companies now offer such a service for a fee that can range upwards of several thousands of dollars. How do such tests work and how valid are they? Furthermore, what do you do if you get bad news or good news? Before long, everyone will be able to sequence his or her entire genome. The hope is that doctors may one day be able to use our genomes to predict who is likely to get sick and what to do to prevent it. But this new era will have to wait until scientists fully untangle the web of genetic and environmental factors that cause most human disease.
Pros and cons of DNA Testing
* The ability to obtain personal genetic information quickly and privately without a “prescription”. The information can include disease predisposition and carrier status.
* This ability to make lifestyle changes, such as diet and exercise, based on the testing results.
* Access to interesting information about ancestry. Some DTC companies offer testing services that will determine the presence and percentage of ethnic, geographic and even Neanderthal DNA.
* The relative affordability of DTC testing compared to other forms of genetic testing. Many companies offer services for a few hundred dollars.
The majority of the drawbacks associated with DTC genetic testing stem from the absence of a medical professional that can help an individual understand the results. Many companies have genetic counselors on staff. However, email and phone exchanges are poor substitutes for a face-to-face discussion. Common misunderstandings regarding genetic testing results include:
* An overestimation of the role genetics plays in disease. The amount that genetics contributes to a trait varies, but very few traits and/or disease are controlled strictly be genes. Most traits are also affected by environmental factors and lifestyle choices.
* Difficulty in interpreting a disease risk. Participants must relay on emails and information on a website to understand their disease risk versus the average population risk. Also, the disease risk presented by DTC companies does not include a timeframe. For some diseases the risk remains low until later in life and then goes up incrementally with age.
* Confusion over the methodology. Not all genetic testing is “created equal”. Genetic tests for diseases that are caused by a known single gene defect can predict with more certainty (sometimes 100%) whether or not an individual will be affected by a disease or is a carrier. Often association studies (GWAS) are employed for diseases in which multiple genes contribute, or no specific gene has been identified. The results from GWAS do not have the same degree of certainty as traditional genetic tests.
* A lack of monitoring of the psychological and emotional status of the participant. Some DTC companies offer genetic tests for life-altering, and even terminal, conditions. Participants may feel a wide range of emotions including anger, depression and guilt after receiving difficult news.
* A lack of oversight of the companies. Because DTC genetics companies are relatively new, the government has not yet determined how to best regulate them. Many companies are reputable and offer quality services with reliable results. Other companies make false claims and use faulty practices. It is up to the consumer to distinguish the good from the bad.
More About DNA Testing
What percentage of our health is dictated by our genetics, and what portion can be attributed to a person’s behavior or environment?
The percentage of our health dictated by our genetics and the faction by behavior and environment depends on individual diseases. Some diseases are entirely genetic and they are called 100 percent penetrant. Diseases such as Huntington’s disease, cystic fibrosis, sickle cell anemia, Tay-Sachs disease and Downs syndrome are purely genetic. Other, more complex diseases such as Type 2 diabetes or rheumatoid arthritis have a significant behavioral component. That means that even if a person has a genetic predisposition towards the disease there is a lot one can do behaviorally to prevent it.
Complex or multifactorial diseases often have several genetic components as well as several behavioral components. For example, there are now at least a dozen known genes that can contribute to Type 2 diabetes. This is because there are many pathways that lead to the disease. Decreased production of insulin, decreased secretion of insulin and decreased response to insulin are the most common. On the other hand, many behavioral aspects can contribute to causing or exacerbating the disease. Obesity and sedentary life style are but two of them. Many other diseases, such as lung cancer, are nearly entirely behavioral. Others, such as most infectious diseases, are entirely environmental.
How can understanding the way specific genetic variants influence individuals’ disease risk enable awareness and possible prevention or treatment?
If someone knows that they have genes predisposing them to a particular disease, then they can be more vigilant to other symptoms of that disease and also discuss further clinical tests for the disease with their doctor. For example, if someone has certain alleles of the gene for clotting factor F5, it could be an indication that the person might be at a high risk of developing deep vein thrombosis (DVT) and one should perform a test of their thrombin levels. This is very important as DVT can lead to strokes and pulmonary embolisms resulting in death.
Other examples are familial breast cancer. If a person has a family history of breast cancer and genetic tests indicate that they have one of the BRCA 1 or BRCA 2 mutations, then they should make sure that they have regular mammography exams. Familial breast cancer is one of the complex diseases that is not 100 percent penetrant. Twenty percent of individuals carrying these mutations will not get breast cancer or ovarian cancer during their entire life. Nevertheless, all such individuals should be much more vigilant than those without these genes.
Finally, if one has two or three of the genes that predispose them to Type 2 diabetes, they should watch their weight, exercise regularly and have their blood glucose measured routinely. Also knowing the type of genetic defects associated with a person’s Type 2 diabetes can help in planning their treatment. There are genetic loci that reduce the number of insulin producing cells in the pancreas that are best treated with drugs that stimulate insulin production from the remaining cells. Obese people often become insulin resistant and they would need a different or additional treatment.
How can knowing one’s own genetic profile help reduce health care costs and motivate patients to make healthier decisions?
Preventive medicine is always the best and least expensive medicine. We currently use vaccines to prevent many infectious diseases. This is far less expensive and much better for the patient than using antibiotic or anti-viral treatments to try to cure an infection. The risks are also substantially lower with vaccines. Much of the cost of the current health care is due to expensive diagnostic methods and interventions for patients who already have a disease. So preventing the disease in the first place is by far, the best way to reduce health care costs.
Hopefully, genomics and genetic testing will do for inherited disease what vaccines have done for infectious disease. I see genomics as being the way toward preventing the manifestations of inherited disease. More importantly, the cost of sequencing is coming down so fast that in the next three to five years we will be able to determine the complete genome sequence of every individual at birth for less than $1,000. This genomic information, coupled with our knowledge of the genes causing disease mentioned above will give people a genetic roadmap of their potential inherited diseases. This will empower doctors to design specific tests for each person to track his progress along their genetic roadmap as well as recommendations for behaviors likely to improve one’s health by dimishing the chance of a given disease.
Preventing disease will also become the responsibility of the patient. He will know what the risks he takes if he smokes, over-eats or leads a sedentary life style. The risks will be personalized based on his own genetics.