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"A recent article in the New York Times highlighted an ongoing problem with the accuracy of vitamin D testing at the largest commercial clinical laboratory, Quest Diagnostics. It has become clear from shared experience among vitamin D experts, including myself, that Quest Diagnostics has a problem with seemingly random over-estimation of vitamin D levels."

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2009 January thevitamindcure Vitamin_D Cure Vitamin_D_Cure blog_article James Dowd 25ohd calcidiol Testing Errors test tests measurement measuring nutrition

Measuring 25-hydroxyvitamin D in a clinical environment: challenges and needs.
Hollis BW.
Am J Clin Nutr. 2008 Aug;88(2):507S-510S. Review.
PMID: 18689391

In this article, I provide an overview of the techniques available for measuring 25(OH)D, compare these techniques with one another, and assess their clinical utility. I also briefly discuss the stability of 25(OH)D in biological media and present an overview of the Vitamin D External Quality Assessment Scheme.

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2008 August ajcn study review measuring measurement test testing 25ohd calcidiol vitamin_D Hollis clinical environment DiaSorin RIA HPLC LC-MS nutrition

Quantifying human calcium absorption using pharmacokinetic methods.
Heaney RP.
J Nutr. 2003 Apr;133(4):1224-6.
PMID: 12672947

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2003 April jn Heaney study research clinical_trial humans men calcium absorption measurement pharmacokinetic methods pharmacokinetics Quantifying nutrition medline

Vitamin D status: measurement, interpretation, and clinical application.
Holick MF.
Ann Epidemiol. 2009 Feb;19(2):73-8. Epub 2008 Mar 10. Review.
PMID: 18329892

Conclusion

The only way to determine whether a person is vitamin D deficient or sufficient is to measure their circulating level of 25(OH)D. There are a variety of assays used to measure 25(OH)D. The radioimmunoassays and competitive protein binding assays for 25(OH)D are useful in detecting vitamin D deficiency and sufficiency. However, these assays are fraught with technical difficulties, especially if they are not run routinely (Fig. 4) (33). Several reference laboratories have now switched to LC-MS ,which measures both 25(OH)D2 and 25(OH)D3 quantitatively. The total 25(OH)D, i.e., 25(OH)D2 plus 25(OH)D3, is what physicians need to be aware of for their patients. A level >30 ng/mL is

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2009 February study review humans Holick vitamin_D status 25ohd Measurement Interpretation Clinical Application sunlight PTH cancer calcitrial assays deficiency insufficiency definition nutrition medline

Einstein called it "spooky action at a distance:" one particle can instantaneously tell what another is doing without being anywhere near it. It's called quantum entanglement. And now NIST physicists have brought this effect to the real world.

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2009 June news quantum entanglement quantum_entanglement physics measure measurement communication distance science NIST faster-than-light particle particles

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A team of chemists has developed a mathematical computer model to measure the "heat" inside a chili pepper, a process that could provide quicker and cheaper information to certain food and drug industries.

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