Charing Cross Hospital recently hosted an update meeting on vitamin D. The meeting included presentations from Graham Carter of the Vitamin D External Quality Assessment Scheme (DEQAS), Imperial College Healthcare who spoke about the performance of laboratory assays for the measurement of 25-hydroxy vitamin D. The DEQAS quality assessment scheme has been operating since 1989 and currently has over 1200 participating laboratories in 54 countries. Graham summarised the performance of the different laboratory assays currently in use. The immunoassays in routine use for the assessment of vitamin D status reliably detect 25-hydroxy vitamin D3 (cholecalciferol); the animal form of vitamin most commonly found in over the counter supplements. For reliable assessment of overall vitamin D status in those patients taking supplements containing 25-hydroxy vitamin D2 (ergocalciferol); the plant form of vitamin D, LC-MS/MS assays are superior. The laboratories at Imperial College Healthcare offer both of these assays for the assessment of vitamin D status.
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DEQAS are currently collaborating with the Office of Dietary Supplements at the National Institutes of Health (NIH-ODS) in the USA on the Vitamin D Standardization Program (VDSP).
Dr Chris Sempos, the VDSP program co-ordinator gave a presentation on the work of the VDSP to date. The goal of the VDSP is to promote the standardized laboratory measurement of total 25-hydroxy vitamin D in order to improve clinical and public health practice worldwide. Standardization is essential to improve the detection, evaluation, and treatment of vitamin D deficiency and insufficiency by making measurements of serum total 25-hydroxyvitamin D [25(OH)D] accurate and comparable over time, location, and laboratory procedure.
Other talks included a presentation by Karen Phinney from the National Institute for Standards and Technology (NIST), USA about the development of a reference measurement procedure for vitamin D binding protein. This assay will enable an evaluation of the accuracy of routine methods for the measurement of vitamin D binding protein. This is an important developing area since it is now known that ethnic differences exist in the levels of this protein and also in the binding affinity for 25-hydroxy vitamin D.
The meeting provided an excellent opportunity for the attending clinicians and scientists to discuss the latest developments in the vitamin D field and was enjoyed by all those who attended.
Emma Walker PhD FRCPath,
Consultant Clinical Scientist, Clinical Biochemistry
Imperial College Healthcare NHS Trust