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New vitamin D tests not accurate as desired

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By David Liu, PHD

Sunday July 1, 2012 (foodconsumer.org) -- New vitamin D tests are not accurate as thought.  They tend to overestimate vitamin D deficiency, according to a new study by researchers of Loyola University Chicago Stritch School of Medicine who presented the findings at ENDO 2012, the 94th Annual Meeting and Expo in Houston.

Earle W. Holmes, PhD, and colleagues examined two new tests Abbott Architect and Siemans Centaur2 by checking on 163 randomly selected blood samples.  They found  in 40 percent of the Abbott Architect specimens and 48 percent of the Siemans Centaur2 specimens, tested vitamin D levels were at least 25 percent too high or 25 percent too low. 

"There has been an exponential increase in the number of vitamin D tests ordered for patients," Holmes said. "But our study of two newly approved tests showed they had pretty poor performance."

The tests tend to result in false positive cases of vitamin D deficiency. The researchers used the LCMS method, which is believed to be accurate, to estimate vitamin D levels in the selected blood specimens and they found 33 of the 163 specimens vitamin D deficient, compared to 45 cases of vitamin D deficiency found by the Abbott test and 71 cases by the Siemens test.

Only a few foods provide vitamin D including cold water oily fish like salmon, eggs and mushroom. The main source of vitamin D is the sunshine.   When a person's hands and face are exposed to the sun at the hottest hours for 15 to 20 minutes, he should have enough vitamin D synthesized in his skin.  But black people are at risk of vitamin D deficiency as it's less effective for their dark skin to absorb uv-rays, which are needed for vitamin D synthesis.

Vitamin D is not just for heathy bone.  It has been found associated with more than 100 health conditions including cancer, heart disease, diabetes, depression, high blood pressure and osteoporosis.

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