Genetic testing company 23AndMe is back with a controversial new offering, after the U.S. Food and Drug Administration on Thursday green-lighted the companys request to market a fresh batch of direct-to-consumer tests. Soon, with a simple saliva swab dropped in the mail, customers will be able to get answers about their genetic risk for developing 10 maladiesincluding Parkinsons disease and late-onset Alzheimers.

The FDA approval will likely reignite a long-simmering debate about when and how such tests should be used. Even when there are strong links between certain gene variants and medical conditions, genetic information often remains difficult to interpret. It must be balanced against other factors including health status, lifestyle and environmental influences, which could sharpen or weaken risk. If disease risk news is delivered at homewithout a genetic counselor or doctor on hand to offer contextmany geneticists fear it can lead to unnecessary stress, confusion and misunderstandings.

Against that backdrop, the FDAs decision came with caveats: Results obtained from the tests should not be used for diagnosis or to inform treatment decisions, the agency said in a statement. It added that false positive and false negative findings are possible.

But geneticist Michael Watson, executive director of the American College of Medical Genetics and Genomics, thinks consumers will have trouble making such distinctions and says he doubts people will view them as a mere novelty. Watson also worries 23AndMes wares may create other problems: Follow-up testing for some of these conditions may be quite pricey, he says, and insurance companies might not cover that cost if a person has no symptoms. He also notes that some of the conditions involved may have no proved treatments, leaving consumers with major concernsand few options to address them, aside from steps like making some lifestyle changes.

The makeup of 23AndMes reports to consumers is still being finalized, but the company says it does not expect to grade or rank a persons risk of developing any of the 10 conditions approved for analysis. Instead it will simply report a person has a gene variant associated with any of the maladies and is at an increased risk, the company told Scientific American.

The FDA decision may significantly widen the companys market and top off a years-long debate about what sort of genetic information should be available to consumers without professional medical oversight. After the FDAs 2013 decision to stop 23AndMe from sharing data about disease risk with its customers, the company was still able to offer them information about their genetic ancestry. It has also been selling consumer tests for genes that would indicate whether people are carriers for more than 30 heritable conditions, including cystic fibrosis and Tay-Sachs disease.

This month 23AndMe plans to release its first set of genetic health-risk reports for late-onset Alzheimers disease, Parkinsons disease, hereditary thrombophilia (a blood-clotting disorder), alpha 1-antitrypsin deficiency (a condition that raises the risk of lung and liver disease), and a new carrier status report for Gauchers disease (an organ and tissue disorder). Reports for other tests will follow, the company says.

In considering whether to approve the tests, the FDA says it reviewed studies that demonstrated the 23AndMe procedures correctly and consistently identified variants associated with the 10 conditions. Further data from peer-reviewed scientific literature demonstrated the links between these gene variants and conditions, and supported the underlying science.

The FDA also announced on Thursday that it plans to offer the company exemptions for similar genetic tests in the future, without requiring them to be submitted for premarket review. That decision could leave the door open to offering tests for other conditions that have questionable reproducibility, says Jim Evans, a genetics and medicine professor at the University of North Carolina School of Medicine.

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Too Much Information? FDA Clears 23AndMe to Sell Home Genetic Tests for Alzheimer's and Parkinson's - Scientific American