Quest Acknowledges Errors in Vitamin D Tests

January 23, 2009 6 min read

Quest Acknowledges Errors in Vitamin D Tests

As I mentioned in my December newsletter on vitamin D, the testing procedure that Quest lab uses for vitamin D (25 hydroxyvitamin D), will give a false reading - 30% higher than the actual vitamin D level. On January 9, 2009, the New York Times reported yet another problem with the testing of vitamin D and many of the tests have been recalled. Apparently the problem reported in the Times article has been resolved but this is a separate issue to the false reading problem.

If you have had your vitamin D tested (25, hydroxyvitamin D) by Quest lab you may want to check with Quest to make sure your test was not one of the ones recalled. Assuming your test was not recalled you have to do some math to arrive at the correct vitamin D level. Divide the number on your lab report by 1.3 to correct for the 30% false high reading. If your lab report is 40 divide by 1.3 - the actual vitamin D is 30.78. This is important because 30 ng/ml is too low and requires supplementation. I am also investigating the assays that Kaiser and other labs use which I will report on in future articles.

Quest Acknowledges Errors in Vitamin D Tests 
The New York Times
January 8, 2009

The nation’s largest medical laboratory company provided possibly erroneous results to thousands of people who had their vitamin D levels tested in the last two years, the company has acknowledged.

The company, Quest Diagnostics, has already sent letters to thousands of doctors listing the patients who might have received “questionable” test results and is offering free retests. The company said it had fixed the problems.

An erroneously high result may mean patients will not take vitamin D supplements when perhaps they should, doctors said. And an erroneously low test result might lead in rare instances to a toxic overdose of vitamin D. When the Quest tests have been inaccurate, the reading has typically been too high, although not in all cases.

Quest’s action represents “the largest patient test recall I’m aware of in my 20 years in the business,” said Robert L. Michel, editor of The Dark Report, a newsletter for pathologists that first reported on Quest’s action.

The incident could raise calls for more regulation of diagnostic testing at a time when diagnostics are playing an increasingly crucial role in guiding medical treatment. Many laboratory tests, including Quest’s vitamin D test, do not require approval from the Food and Drug Administration.

The incident also raises questions about vitamin D testing, which has surged because studies have suggested that a deficiency of the nutrient raises the risk of bone weakness, cancer, heart attacks, autoimmune diseases and other illnesses. Quest and other laboratories have reported that in some cases test volumes had nearly doubled from one year to the next. Medicare pays about $40 for a vitamin D test, though doctors say some of their patients were billed as much as $200 for the Quest test.

But experts say that so far there is no standardization of the tests, meaning that results can differ considerably from one laboratory to another.

That can make it hard for doctors to decide on treatment and for experts to compare studies aimed at determining the optimal level of vitamin D in the blood. “If you get your vitamin D level measured in the Mayo Clinic, the Cleveland Clinic and the Timbuktu Clinic, it would be nice if it came out the same value,” said Dr. Neil C. Binkley, associate professor of medicine at the University of Wisconsin.

Dr. Binkley said that a few years ago he sent a sample of his blood to six laboratories and got results that ranged from 14 nanograms a milliliter, which would be a deficient level, to 41 nanograms — a level three times as high and considered adequate. While the tests’ consistency has improved since then, there can still be substantial variability, he said.

Yet many experts say that even if the tests were accurate, there would still be uncertainty in how to treat patients. There is considerable debate about how much vitamin D is needed and whether vitamin D supplements even prevent various diseases. Vitamin D is usually made by the body when the skin is exposed to sunlight and is also contained in oily fish and some fortified drinks like milk.

Some doctors said they had switched to other testing laboratories because of Quest’s problems. But Quest, based in Madison, N.J., offers numerous tests, from routine blood work to sophisticated genetic tests. No one type of test represents a large potion of its revenue, which was $5.45 billion for the first nine months of 2008.

The company said the retesting would not have a material effect on its earnings. The company’s stock price rose 80 cents Wednesday to $49.20, approximately in the middle of its 52-week range.

Quest’s problems with the vitamin D analysis arose after it shifted in 2006 and 2007 to a new test of its own design, replacing an older F.D.A.-approved test. The new test promised to be more accurate and offer more detailed information, Quest executives said. But the test relied on a sophisticated instrument called a mass spectrometer, which can be tricky to use, especially for high-volume testing.

Dr. Wael A. Salameh, the medical director for endocrinology at Quest’s most sophisticated laboratory, which is in San Juan Capistrano, Calif., said some materials used to calibrate test results had been faulty. And four of the seven Quest testing laboratories around the country did not always follow proper procedures, he said.

Quest would not say how many patients were affected. But a spokesman did not deny that thousands of doctors were sent letters in October. Each doctor had at least one patient, and in many cases dozens of patients, who had a possibly inaccurate test result. Dr. Salameh said the inaccurate results represented less than 10 percent of all the vitamin D tests done by Quest from early 2007 to mid-2008. And even many of the possibly inaccurate results were probably accurate, he said, because Quest sent letters even if there was only a remote chance that the test was erroneous.

“We are kind of being penalized for going the extra mile,” he said.

Dr. Ronald L. Hoffman, a clinical nutritionist in New York City, said his letter from Quest mentioned about two dozen of his patients. “There was a patient we put on vitamin D and all of a sudden, for the first time ever, the patient came back with what seemed to be a toxic level of vitamin D,” said Dr. Hoffman, who is also host of a radio program on health, on WOR in New York City. When the patient was given a different vitamin D test, the value was considerably lower.

Dr. Lawrence D. Rosen, a pediatrician in Oradell, N.J., who treats many autistic children, said his letter named more than 20 patients and that retesting was an inconvenience. “A lot of these kids, especially if they’re autistic, it’s a big deal for parents to have their blood drawn,” he said.

One question is why Quest’s problems took so long to discover. Some doctors who advocate vitamin D use said they had begun noticing some unusually high test results in 2007 and had begun complaining publicly in the summer of 2008.

One of them was Dr. John J. Cannell, a psychiatrist at a California hospital for the criminally insane who started the Vitamin D Council to promote use of the vitamin. He said that after the test was introduced, he started noticing that some patients had normal levels of vitamin D, a departure from the past, when the levels had often been low.

“A black man coming from solitary confinement on C.D.C.R. food cannot have a normal level of vitamin D,” he said, referring to the California Department of Corrections and Rehabilitation. People with dark skin do not convert sunlight to vitamin D as easily as those with lighter skin.

Quest executives say they dismissed the concerns of Dr. Cannell because he was a paid consultant to DiaSorin, a company that makes a rival test.

They said the company’s review of its testing results had instead been prompted mainly by its own review of national health trends based on Quest data, which had shown an unusual rise in average vitamin D levels.

Meanwhile, the F.D.A. is considering increasing its role in regulating diagnostic tests. Now, test kits sold to labs, hospitals and doctor’s offices must be approved by the agency. But tests developed and offered by a single laboratory, like the Quest vitamin D test, do not.

Quest and many other laboratories argue that lab quality is already regulated through Medicare and that having to win approval for each new test will slow innovation and raise costs.