Ounces of Prevention – Genetic Disease Testing

Actress Angelina Jolie, it could safely be said, has one of the most admired figures in the world. It is then understandable that her recent decision to undergo a double mastectomy also received a great deal of attention. Jolie chose to have the procedure after a genetic screen revealed that she carries a rare variant of the BRCA1 gene associated with a greatly increased risk of breast cancer. The spotlight attached to such a high-profile celebrity has been turned on genetic testing, much like attention was given to colonoscopies after Katie Couric of the Today Show broadcast her own, and many women are now considering tests for BRCA and other potentially harmful mutations.

A 23andme testing kit, courtesy of Paul Stamatiou.

The market is certainly willing to provide these sorts of tests, many of them without the consultation of a medical professional. 23andMe, for example, provides a self-administered kit for $99 that screens for over 240 health conditions,  while GenePlanet offers a comprehensive analysis of disease risk and drug interactions for €499. These tests operate using relative inexpensive SNP (single nucleotide polymorphism) techniques; in essence, they search for a difference in one “letter” of the genetic code that has previously been associated with a given health condition. Many of the tests used in a hospital setting, however, involve the sequencing of at-risk genes, reading the full “sentence” of the DNA that codes for a protein or regulates other parts of the code. These tests can be quite pricey: Myriad Genetics, the company behind Jolie’s BRCA testing, charges up to $4,000 for its most comprehensive examination of breast cancer risk. Myriad currently holds patents on the BRCA genes, granting it a monopoly on tests for harmful mutations (a monopoly currently being challenged in the Supreme Court).

These kinds of price tags, which in many cases may not be covered by insurance, have caused some doctors to question whether the enthusiasm for genetic testing may be premature. A pressing issue for many is that, while testing may provide information on disease risks, in most cases there are few preventative actions that can be taken. Mastectomy and breast cancer is an obvious exception, but as Stanford University’s Andrew Fire has been quoted, “if someone off the street is looking for pointers on how to live a healthier life, there’s nothing these tests will tell you besides basic physician advice like ‘eat right, don’t smoke and get plenty of exercise.’” For genetic tests of conditions like Lou Gehrig’s disease or Parkinson’s disease, a positive result can at present yield little but stress and referral to genetic counseling. In the future, it may become possible to replace faulty regions of the genome in a process called gene therapy, but the science of this technique, while promising, is still very much in the exploratory phase.

However, a powerful reason for more widespread genetic testing is that these tests become more powerful the more they are administered. SNP tests work by correlating differences in DNA with diseases; these correlations are not perfect, as many other factors are usually involved in the development of a disease. Yet after a person is tested for a given SNP, whether they develop a given disease becomes a data point for the interpretation of that genetic variant. The statistical strength of the test increases with the sample size, making predictions for other patients more accurate. Those who undergo testing today are laying the groundwork for the future, where it may be possible to do more about the results than wait and worry. Each individual must weigh whether that contribution to science is worth the potential pain of learning about a disease for which little can currently be done.

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2 thoughts on “Ounces of Prevention – Genetic Disease Testing

  1. Pingback: Don't Fall for Genetic Screening

  2. Pingback: swordofscience | Follow-Up: Genetic Disease Testing and the FDA

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