Vitamin D Test Reliability

This is an excerpt from Dr. Cannell's excellent vitamin D newsletter. It is important to note that all test results can have errors, even DEXA scores, so use numbers as a guide not as an absolute.

"Robert Michel, publisher of the Dark Report, just reported on his latest experience with Vitamin D testing. The results are not good, especially for Quest Diagnostics. Michel sent 24 aliquots, or identical samples, of his blood, all drawn the same day, to two different reference labs, which in turn sent them, over a three week period, for 24 Vitamin D blood tests. Again, 24 blood samples, drawn from the same person at the same time, so, in a perfect world, all 24 samples would test the same.

However, the results varied from 36 ng/ml to 66 ng/ml! Quest’s results: 36, 42, 51, 54, 55, and 66. The Mayo Clinic, which uses the same technique that Quest uses, did better, 48, 48, 51, and 61. The good news was the immunoassay methods used by LabCorp, Clinical Pathology Labs, and ARUP clustered around 44 ng/ml and all 11 samples were within 4 points of 44 ng/ml with the highest 48 and the lowest 39.6.

Long story short, if you use Quest Diagnostics, divide by 1.3 and hope they continue to work at improving their process. Mayo’s is better but Dr. Singh must be getting tired of all those Vitamin D tests, which are hard to do on mass spec. If your lab sends out to LabCorp, ARUP, or Clinical Pathology Labs, you are fine."

You can sign-up for Dr. Cannell’s newsletter at his website for vitamin D at www.vitamindcouncil.org.

If you have further questions or if you want to join our support group please feel free to email me at bebonestrong@sequoiahealth.com.

Woody McMahon