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Contemporary Diagnosis and Treatment of Vitamin D–Related Disorders
Author(s) -
Jones Glenville,
Horst Ronald,
Carter Graham,
Makin Hugh LJ
Publication year - 2007
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.07s219
Subject(s) - vitamin d and neurology , quality assurance , calcitriol , radioimmunoassay , vitamin d binding protein , biomarker , competitive binding , medicine , high performance liquid chromatography , chromatography , chemistry , biochemistry , external quality assessment , pathology , receptor
Plasma 25(OH)D has emerged as a valuable biomarker for the many varied health‐related effects of vitamin D in the clinic mainly because of the recognition of the importance of the enzyme, CYP27B1, or the 25(OH)D‐α‐hydroxylase in the extrarenal, target cell production of calcitriol. This review briefly assesses current methodology for plasma 25(OH)D assay focusing mainly on currrent controversies surrounding the definition of the normal range and performance characteristics of the assay, separate measurement of both 25(OH)D 2 and 25(OH)D 3 , and quality assurance tesing of laboratories offering the test. Clinicians have two main types of 25(OH)D assay based on either high‐performance liquid chromatography with UV or mass detection or higher throughput kits based on protein (competitive protein binding assay or radioimmunoassay) binding. Based on 30 yr of experience with measuring 25(OH)D levels, it is concluded that, in the hands of appropriately trained experts, both types of assay provide reliable and accurate results, but all laboratories providing 25(OH)D data need frequent external quality assurance service to ensure that this performance is maintained.