A little genetic knowledge not necessarily a good thing

Personalized medicine, drugs tailored to your specific genetic makeup, all your risk factors reduced to a panel or chip. It all sounds so wonderful. Scientists are unraveling new genetic markers for diseases rare and common every day.

But many genetic researchers and even more doctors are concerned that for patients and medicos alike, a little genetic knowledge may not necessarily be a good thing.

Technology to identify genes that increase the risk for one or more medical problems and to screen individuals' maps, or genomes, for those genes has galloped ahead of medicine's ability to interpret many findings.

Even if you know you carry one or more genes that increase your risk for a disease, you and your doctor still may not know what to do about it.

Genomic medicine can and does hit home runs in identifying conditions caused by a single gene that malfunctions. There are more than 6,000 known single-gene disorders, including cystic fibrosis, sickle-cell anemia, Huntingdon's disease and hereditary hemochromatosis (excessive iron buildup in blood cells).

In many cases, early diagnosis offers faster, better treatment and improved outcomes for patients in the long term, even as researchers continue to look for avenues to prevent or even cure the illnesses.

Things are a lot more complicated when it comes to fingering genes behind the more common chronic afflictions, such as heart disease, stroke, diabetes, cancer, osteoporosis, obesity and depression.

Researchers believe there are many genes, maybe hundreds, that might play a role for increased or decreased risk for those conditions, and they're only beginning to understand how the different genes and the proteins they produce interact.

Likewise, scientists are only starting to understand how people carrying certain genes are likely to react positively or negatively to drugs, with the U.S. Food and Drug Administration encouraging tests for a handful of prescriptions so far.

So, while the Journal of the American Medical Association devoted most of this week's issue to reports highlighting advances in genetic medicine, it also featured authors urging a bit of caution and more efforts to educate the medical profession and the public on genetic medicine.

A big concern is the explosion of genetic tests being marketed directly to the public by private labs. Some offer "whole genome" scans for $1,000 or more. Others focus on genes linked to specific types of cancer. Still others produce a genetic profile coupled with recommendations for the use of certain skin products or diets.

There is little government regulation of such tests and the scientific credentials are often murky, although many are offshoots of academic research. Experts note that there are likely to be numerous false-positive results when thousands of genetic markers are probed at once.

"The implicit marketing strategy is to involve the consumer in a 'voyage of genetic self-discovery' -- even if some of the initial paths charted lead nowhere," wrote Dr. Kenneth Offit, a genetic specialist at Memorial Sloan-Kettering Cancer Center in New York City.

"In the worst-case scenario, the paths may lead to unnecessary medical interventions or false reassurances and missed diagnoses."

Ideally, at least, genetic testing ordered by a doctor is carefully reviewed and followed up with specialized counseling, although counselors admit there are too few of them to always meet personally with patients to go over results.

But doctors whose patients present them with genetic-risk reports often have little or no information to help them interpret what the findings mean for health, or even if the scans are valid.

Dr. Maren Scheuner, a researcher with the Rand Corp., and colleagues published a review of genetic-medicine research done over the past eight years.

"Our most important and consistent finding is that the primary care work force, which will be required to be on the front lines of the integration of genomics into the regular practice of medicine, feels woefully underprepared to do so," she wrote.

On the Net: http://www.jama.com

(Distributed by Scripps Howard News Service, http://www.scrippsnews.net)