vitamin D, sunshine, sunlight, quest, lab corpThe nation’s largest medical laboratory company, Quest Diagnostics, gave potentially erroneous results to thousands of people who had their vitamin D levels tested in the last two years. The company has already sent letters to thousands of doctors listing the patients who might have received questionable test results and is offering free retests.
An erroneously high result could lead to vitamin D deficiency going undetected, and an erroneously low test result could possibly lead to a toxic overdose of vitamin D. When the Quest tests have been inaccurate, the reading has typically been too high.
The incident could raise calls for more regulation of diagnostic testing by the FDA, especially as diagnostics play an increasingly crucial role in guiding medical treatment. It 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.
* New York Times January 7, 2009
Dr. Mercola Dr. Mercola's Comments:
If you keep pushing hard enough, frequently you can achieve results. This is what appears to have happened here. Thanks to Dr. John Cannell and my site, one of the lab industry’s leaders wrote a scathing report of Quest’s vitamin D testing failures that was widely circulated in the lab and financial community, which prompted this article in the NY Times.
Quest Diagnostics admitted publicly that, for 18 months in 2007 and 2009, it had systemic failures in its vitamin D testing. However, Quest maintained in its statements to the National media that this was a "small problem" and, "it had not been made aware that any patient was harmed" by the inaccurate vitamin D tests it had reported.
However, many physicians like myself, recognized these problems and contacted Quest about their concerns. The Dark Report is preparing to publicize the negative impact that delivering hundreds of thousands of inaccurate test results for almost two years had on physicians and patients.
You Can Help!!!
To document these facts, The Dark Report wants copies (with patient data blacked out) of 2007 and 2008 Quest vitamin D reports with test results that were recognized as wrong by physicians. Of greatest value are test results by Quest and Labcorp on the same patient which clearly shows the problem with Quest's vitamin D tests.
Physicians who would like to share their experiences and how their medical practice was disrupted by Quest's inaccurate tests in 2007 and 2008 can contact editor Robert Michel by emailing firstname.lastname@example.org. If you request it, he will send you the full issue of The Dark Report which details the systemic failures with Quest Diagnostics' vitamin D tests.
Patients who have seen adverse consequences because of inaccurate vitamin D test results from Quest diagnostics are also invited to email their stories to email@example.com.
This is a particularly tragic story because there has been an enormous amount of research on vitamin D in the past couple of years that unequivocally validates its major role in most all chronic disease.
Already, vitamin D deficiency has been linked to ailments and diseases such as:
* Flu and other infections
* Diabetes 1 and 2
These new findings have fueled a massive surge in vitamin D testing. The good news is that the message is getting out and physicians are actually testing for vitamin D now, so much so that by some estimates, Quest alone is doing half a million tests per month.
The bad news is that Quest has a flawed vitamin D test and methodology. I first became aware of the problem with Quest’s test results back in September of last year, at which point I issued a warning about the irregularities in their test values, and what this means to your health.
The primary problem with the far more expensive and sophisticated test that Quest uses to measure vitamin D is that it has a low degree of automation, and thus requires highly skilled analytical chemists to run properly. As a result of this, many of the tests are simply not done properly. But the more important issue is that even when it is run properly the results are elevated by approximately 40 percent over the DiaSorin -- a highly reproducible and automated assay used by Lab Corp.
So, if you have a Quest result you will need to multiply the result by 0.6 to come closer to reality.
What’s the Problem with Quest’s Test?
Between 2006 and 2007, Quest shifted over to using a new test of its own design, which was supposed to be more accurate and detailed. However, this test relies on mass spectrometry, which involves a rather sophisticated instrument that requires highly skilled lab workers and is ill suited for high-volume testing.
The gold standard in vitamin D testing is DiaSorin. Their radioimmunoassay (RIA) method for measuring total vitamin D levels has become the gold standard not because it’s more accurate than the others, but because it’s the one used in almost every major vitamin D study, on which the recommended blood levels for clinical efficacy are based.
Therefore, in order for any other testing method to offer clinically relevant results, the test values must agree with DiaSorin RIA results, since those were used to establish the recommended levels.
Unfortunately, Quest did not calibrate their test results against DiaSorin. So, when done properly it is analytically accurate, their test has given vitamin D values that are consistently about 25-40 percent higher than the DiaSorin assay. This can obviously give you the FALSE reassurance that your levels are healthy, or even toxic, leading you to discontinue treatment when in fact you still need more vitamin D.
As a result of the inconsistencies with Quest’s tests, thousands of physicians across the U.S. were sent letters in October 2008 stating the tests performed for their patients may have been inaccurate and needed to be redone. Since many patients are tested for vitamin D at my clinic, I received hundreds of these letters.
This failure within Quest is without precedent! Never before has a lab admitted to making mistakes on such a large scale. What most physicians don’t appreciate is that by notifying them of "questionable results" and leaving the authorization for the retests up to the physician, Quest transferred much of its liability back to the ordering physicians! By sending the letters to the physicians, Quest made it the doctor’s responsibility to contact the patient.
This maneuver limits their potential litigation and massive class action lawsuits, and I suspect that was a strong consideration in their sending these letters.
And a warning to you patients who, during 2007 and 2008 got vitamin D results from Quest and recognized them to be inconsistent with past history and current expectations. If your doctor either forgets to notify you, or decides not to authorize your retest, you would never know that during those 18 months, you may have received inaccurate vitamin D tests.
What is Your Optimal Vitamin D Level?
It’s important to note that although your physician may state that your levels are “normal,” it does not mean that you are in the optimal range – the range you need to be in to actually achieve the kinds of health benefits found in clinical research.
Additionally, recent research findings have led to the optimal vitamin D levels being raised even higher than before.
The optimal values in the chart below show the increased values you’ll want to keep in mind. These values have been confirmed by more recent studies into vitamin D status and its effects on health and reduced disease risks.
So, if you have the above test performed, please realize that many commercial labs are using the older, dated reference ranges. The above values are the most recent ones based on large-scale clinical research findings.
Which Lab Should You Use?
First of all, vitamin D status is measured by looking at blood levels of 25-hydroxyvitamin D3. There are three common methods used for measuring vitamin D3:
1. LC-MS/MS -- This test measures 25-hydroxyvitamin D2 and D3 separately
2. RIA (DiaSorin) -- Developed in 1985, it accurately measures total 25-hydroxyvitamin D (It does not separate D2 and D3)
3. Liaison (DiaSorin) -- a more recently developed automated immunoassay by DiaSorin that has largely replaced the RIA
The LC-MS/MS (liquid chromotatography-mass spectrometry) method is the preferred method for many labs, including the Mayo Clinic, Quest Labs, Esoterix, ZRT, and others, while Liaison is favored by other testing labs like LabCorp.
The LC-MS/MS is clearly a highly accurate test, but only in the hands of experienced technicians who have the time to do the test properly, and only if it’s calibrated against the RIA.
Liaison, which is a more recently developed DiaSorin test that renders clinically accurate results, is a much more accurate testing method for high volume throughput of tests, and does not depend as much on lab technician’s expertise.
LabCorp uses this method, which makes them better able to handle large volumes of tests without sacrificing clinical accuracy or worrying about the qualifications of the staff.
Additionally the charge for the Lab Corp test should be less than half of that of the Quest test.
For all these reasons I now strongly recommend using LabCorp for these reasons until Quest can guarantee accurate, usable results.