ROCHESTER, Minn -- November 6, 2009 -- Results of a long QT syndrome (LQTS) study published in the current issue of the journal Circulation play an important role in understanding genetic testing's role in diagnosing disease.
For the study, Michael Ackerman, MD, Mayo Clinic, Rochester, Minnesota, and colleagues tested nearly 400 patients with a strong clinical diagnosis of LQTS and nearly 1,400 healthy volunteers.
Genetic testing results showed that there was a 'background noise' rate of rare variants present in about 4% of the healthy volunteers, and that the mutation type and location are critical determinants to distinguish this background noise from true LQTS-causing mutations.
"This study demonstrates what we've long suspected in genetic testing circles - that genetic tests are not merely binary tests but are probabilistic tests whereby some test results are going to provide 'no-doubt-about-it' disease mutations, whereas other test results may report a mutation whose pathogenicity is uncertain," said Dr. Ackerman.
"Our research shows that genetic testing is just one piece of the diagnostic puzzle that a physician needs to look at."
The results showed that genetic testing does not always give a yes or no answer for LQTS or other diseases, and it means that physicians need to meticulously interpret genetic test results with the same scrutiny and tenacity as any other diagnostic test such as the electrocardiogram, he said..
Surprisingly, although there are nearly 1,500 genetic tests that physicians can order for patients, this genetic 'signal-to-noise' ratio has been exposed for only a small handful of them, including breast cancer genetic testing and now long QT syndrome testing.
For personalised, individualised medicine to succeed, the medical community must begin to grasp the probabilistic nature of genetic testing, said Dr. Ackerman.
SOURCE: Mayo Clinic
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