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Article: Underestimation of Serum 25-Hydroxyvitamin D by the Nichols Advantage Assay in Patients Receiving Vitamin D Replacement Therapy
- Article from:
- Clinical Chemistry
- Article date:
- June 1, 2005
- Author:
CopyrightCopyright American Association for Clinical Chemistry Jun 2005. Provided by ProQuest LLC. (Hide copyright information)
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To the Editor:
Measurement of 25-hydroxyvitamin D (25OHD) is used to assess both vitamin D status and the response to exogenous replacement therapy (1). Inaccurate assays may place patients at risk of either under- or overreplacement, with potential adverse consequences (1, 2).
Significant interassay and interlaboratory variations in measured 25OHD values have been reported (3, 4). The international Vitamin D Quality Assessment Scheme (DEQAS) monitors the performance of vitamin D assays in >100 laboratories in 18 countries (4). Recently, the analysis of samples containing only 25OHD3 was reported by DEQAS to be within 7% of the target value (as determined by gas chromatography-mass ...