Whether it's out of a less-than-healthy sense of hypochondria or a healthier desire to stay on top of things that affect our health, people are naturally curious about their risk of developing certain diseases. That, after all, is why we see our doctors regularly, so that they can hopefully detect the early signs of a disorder before it develops into something more serious.
Some of the disorders and diseases that could possibly affect us are genetic, meaning that the story of whether we have a predisposition to develop these diseases in there in our genes, theoretically just waiting to be discovered. In the past, though, genetic testing was terribly expensive, conducted at only a few laboratories, and thus out of reach of the normal, health-conscious consumer.
A new generation of mail-order genetic tests has changed all of that. Now, instead of having to have a doctor draw a blood sample and then rush it to a specialized lab for analysis, you can swab the inside of your cheek or spit into a tube and send it through the mail to a lab that will run a series of genetic tests on the sample, and report its findings back to you. These mail-order genetic tests are still not cheap (their cost is usually several hundred dollars), a fact that still places them out of the reach of many consumers, especially because the cost of them is rarely reimbursed by health insurance plans. So are they worth it?
The pros and cons of mail-order genetic testing
On the plus side, such tests can detect genetic markers called SNPs (single nucleotide polymorphisms) that indicate that the person carrying these markers is more susceptible to certain diseases than other people. The SNPs do not cause the diseases in question, but have been shown in clinical trials to be strongly associated with the diseases.
On the con side, the results of a test that indicates you are at a higher-than-average risk of getting a certain disease does not indicate that you'll get that disease. Neither does having a lack of genetic markers for a certain disease mean that you won't get it. All that the presence of a particular SNP indicates is a higher risk of contracting the disease associated with it.
Also on the con side, some of the genetic testing labs may be engaged in a bit of a "con" themselves; in studies performed by the U.S. General Accounting Office, many of the results of the mail-order tests are inaccurate or misleading, which could result in either false fears or equally false hopes on the part of the person being tested.
So the question of whether to invest in such genetic tests is still an individual one. If you know already that your family has a history of certain genetic diseases such as Parkinson's disease or bipolar disorder, you may feel it is worth the several hundred dollars to find out whether you carry that gene. In some cases, knowing that you carry an SNP can help you to make lifestyle changes to decrease the risk of contracting the disease with which it is associated, but in other cases, there are no proactive measures you could take.
If you are considering genetic testing, this is what they can test FOR
If you're thinking that genetic testing can predict your risk for heart disease, save your money; it can't. But it can find SNPs for the following diseases, and information about your potential risk of contracting those diseases may be useful to you:
• Breast cancer and ovarian cancer. First, of the over 200,000 cases of these diseases diagnosed each year, only 5-10% of them can be linked to a family history of the disease, as indicated by mutations of the BRCA1 and BRCA2 genes. These are genes associated with the suppression of tumors, so if mutated, uncontrolled cell growth may occur. Women carrying these gene mutations are 5 times more likely to develop breast cancer and 15-40 times more likely to develop ovarian cancer. But since these mutations mainly appear in women of Ashkenazi Jewish heritage, you're not likely to carry them unless you are from that heritage.
• Bipolar disorder. A mental illness also known as manic-depressive disorder, this condition is characterized by severe mood swings between euphoria and despair, and affects an estimated 5.7 million Americans. Bipolar disorder has a strong genetic component, but researchers have so far found SNPs that account for only a fraction of the cases. The risk for this disorder seems to be more related to how many relatives had it; you have a 70% higher risk for the disorder if your identical twin had it, a 50% higher risk if both parents had it, and a 13% higher risk if only one sibling had it. That said, the average person's risk of developing bipolar disorder is only 2-3%, so genetic testing may not be worth it unless you know there is a family history.
• Obesity. Some genetic scientists attribute heredity as a factor in 84% of the cases of obesity, but the genetic factors that lead to obesity are not fully understood. Genetic tests can detect the presence of a variation of the FTO gene, which seems to be strongly linked with obesity, but the other SNPs are still a mystery.
• Parkinson's disease. This is a more serious neurological disorder with a strong genetic component. The average person's relative risk of contracting it is only 1-2%, but the presence of certain SNPs can raise the risk of contracting it by age 59 to 28% and the risk of contracting it by age 79 to 74%. So if you know that you have a family history of Parkinson's disease, genetic testing may be a good choice, to see whether you were passed the LRRK2 genes in question. Again, their presence does not mean that you'll get the disease, merely that you have a higher risk of doing so.
• AMD (Age-related macular degeneration). This is one of the biggest causes of irreversible blindness, caused by a deterioration of the retina. Genetic tests can detect the presence of a group of ABCR genes, and people with certain variations in these genes have a 30% higher relative risk of developing AMD.
• Psoriasis. While hardly life threatening, psoriasis (red, scaly lesions on many parts of the body) can be uncomfortable, and are up to 80% attributable to variations in a gene called HLA-C. However, only 10% of people carrying this gene variation actually develop psoriasis, and even in those cases some environmental factor needs to be present to trigger it.