Vitamin D Test Errors

By Margarita Nahapetyan

Quest Diagnostics Inc., the world's largest provider of medical diagnostic tests, which has locations nationwide, admitted on Thursday that it provided possibly wrong and inaccurate vitamin D test results to thousands of people over the past two-year period. The Lenexa-based clinical division of Quest Diagnostics, located in Madison, NJ, has about seven labs that perform the tests, and about half of them were involved. Quest collects medical samples from hospitals, doctors' offices and clinics for tests to diagnose medical conditions. More than 43,000 people worldwide are employed by the company.

The error became evident when doctors started having suspicions regarding the test results of some of their patients. It was then that the company started investigating the issue and has been able to identify what caused the errors and has already fixed them. According to Quest's endocrinologist and medical director of the endocrine laboratory Dr. Wael Salameh, the mistakes, on one hand, were caused by the test's "reagents and calibrators," which involved some chemical used in the testing, and, on the other hand, there was "improper follow-up according to standard operating procedure in some laboratories." Salameh was reluctant to say how many vitamin D tests are involved in the potentially inaccurate test results or how much re-testing will cost, but he said the inaccurate results represented less than 10 percent of all the vitamin D tests done by Quest from early 2007 to mid-2008.

An erroneously high test result means that patients will not take vitamin D supplements when they are in need of them, physicians said. And an erroneously low test result might lead in rare cases in a toxic overdose of vitamin D. Symptoms of a vitamin D overdose may include confusion, muscle aching, very vague symptoms. When the Quest Diagnostics tests have been erroneous, the reading has typically been too high, although not in all cases. Subsequently Quest sent letters to all the physicians who might have received "questionable" test results of their patients and offered for them to be re-tested without any charge. Each doctor had at least one patient, and in many cases dozens of patients, who had a possibly inaccurate test result. The company expects the number of actual errors to be much lower after re-tests are done, based on it's internal analysis.

People produce vitamin D, an essential nutrient, when they're exposed to the sun. They also get it from foods, such as bread, orange juice, fortified milk, cereals, fatty fish such as salmon and mackerel, and from nutritional supplements. Vitamin D maintains normal phosphorus and calcium blood levels, helps in the absorption of calcium, which in its turn develops and maintains stronger bones. Vitamin D protects against osteoporosis, high blood pressure and some auto-immune disorders. Vitamin D deficiency could lead to weak bones - a condition called rickets, in children, which can cause fractures, skeletal deformation. As to adults, lack of Vitamin D can cause osteomalacia, which means muscular weakness and weak bones, and those suffering from inflammatory bowel disease are at greatest risk for Vitamin D deficiency. Not enough Vitamin D can also contribute to heart attacks and cancer.

Joan Lappe, professor of nursing and medicine at Creighton University in Omaha, Nebraska, said that the mistake of the tests by Quest Diagnostics company should normally pose no risks on people undergoing them. No incident cases have been mentioned of people who stopped taking Vitamin D for a few days because the results of the tests showed their level was too high or in the case when people took too much of the Vitamin D.

So, what is the recommended level of vitamin D? Most doctors recommend 200 units daily of the vitamin in children and adults up to age 50, and 400 to 600 units for older adults. However, these quantities are far below, according to some doctors who suggest higher levels for some of their patients - up to 1000 units daily and vitamin supplements as well. And new guidelines from the American Academy of Pediatrics recommend children receive 400 IU (international units) of daily vitamin D, way much more than previous recommendations.

Meanwhile, the F.D.A wants to expand its regulation of all diagnostic tests. At this point, test kits which are being sold to laboratories, physicians' offices and hospitals must be approved by the agency. But tests offered by a single lab, like the Quest Diagnostics Vitamin D test, are not. Such single labs say that their work is already regulated by Medicare and protest against waiting for an approval for every single new test. They say it will raise costs and significantly slow down innovation.