WASHINGTON - The largest U.S. medical lab company says it recently discovered and fixed a problem that led to inaccuracies in a small number of tests for vitamin D deficiency.
Quest Diagnostics of Madison, New Jersey, notified thousands of doctors in the fall that it had found the problem.
Gary Samuels, the company's vice president for communications, says the company then offered free tests for patients whose results were deemed questionable.
Blood tests to check levels of vitamin D are on the rise because of research showing a possible link between too little of the "sunshine vitamin" and a higher risk of cancer or heart disease.
People normally get vitamin D from exposure to the sun or from fortified milk, orange juice and cereals. It helps build strong bones.
However, recent research, which still is being debated, suggests it also may play a broader role in protecting against a number of diseases.
"Last year, we did have an issue in a few of our labs that affected a small minority of tests in those labs," Samuels said in an interview this week.
"We identified the problem ourselves. We corrected the problem. We notified doctors and other customers and offered free retesting."
Quest, which reported more than $6 billion in sales last year, is the largest provider of medical laboratory tests in the U.S.
The company has reported double-digit sales growth for its vitamin D tests in recent quarters.
Quest collects medical samples from hospitals, doctors' offices and clinics for tests to diagnose medical conditions. It employs more than 43,000 people worldwide.
Dr. Wael Salameh, a senior medical official with Quest, said internal monitoring picked up hints of a problem during the summer - an "upward trend" in the vitamin D levels being registered by some of its tests.
"That tipped us off," Salameh said.
Eventually, the company flagged about seven per cent of vitamin D testing results from 2007-2008 as questionable, although it believes the problem was much smaller.
Generally, the readings obtained on the questionable tests were higher than they should have been, Salameh said. In some cases, though, it was hard to discern a pattern.
Salameh said he doubted that patients would have suffered any harm from the problem.
People with serious vitamin D deficiency have physical symptoms such as fractures that their doctors would have noticed.
"A good doctor would question the test," Salameh said. "For the few vulnerable patients, other indicators would have flagged the situation to their physician."
Quest officials said the cause of the problem turned out to be the way some of the company's labs were mixing chemicals used in the tests.
But the company also is using a new testing technology, which is the subject of sharp debate within the industry. Critics say the method tends to produce vitamin D readings that are higher than warranted.
Aetna, the insurer, said it was notified by Quest about the problem on Oct. 8.
"We did not, however, see any immediate health issues ... that would have required additional action or intervention on our part," spokeswoman Wendy Morphew said in a statement. "We have not received any significant member inquiries on this matter."
