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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Ruminant Diseases and Immunology Research » Research » Publications at this Location » Publication #193541
Title: THE ASSESSMENT OF CIRCULATING 25(OH)D AND 1,25(OH)2D: WHERE WE ARE AND WHERE WE ARE GOING

Author
item HOLLIS, BRUCE - UNIV SOUTH CAROLINA
item Horst, Ronald

Submitted to: The Journal of Steroid Biochemistry and Molecular Biology
Publication Type: Other
Publication Acceptance Date: 3/17/2006
Publication Date: 3/20/2007
Citation: Hollis, B.W., Horst, R.L. 2007. The assessment of circulating 25(OH)D and 1,25(OH)2D: Where we are and where we are going. Journal of Steroid Biochemistry and Molecular Biology. 103:473-476.

Interpretive Summary:

Technical Abstract: Amongst the major factors responsible for the explosion of knowledge related to Vitamin D metabolism and its relation to clinical disease was the introduction of competitive protein-binding assays (CPBA) for 25(OH)D and 1,25(OH)2D. These assays were based on 3H-reporters and involved chromatographic purification of the sample to be valid. The next generation of assays involved the use of high pressure liquid chromatography (HPLC) which is considered by some to be the “gold standard” for 25(OH)D quantitation. However, the more recent demand for higher throughput formats has resulted in the development of antibody-based assays, incorporating 125I-reporters as well as enzyme-linked reporters. Also, recently introduced into the reference laboratory and perhaps the most significant advancement to date is the LC-MS/MS assay for 25(OH)D. The most recent assays for 25(OH)D are direct serum assays in a high throughput random access format, notably the Nichols Advantage 25(OH)D CPBA and the DiaSorin Liaison 25(OH)D RIA. These assays provide high throughput, up to 180 assays/hr, with little user intervention. The Advantage CPBA has had trouble identifying 25(OH)D2 in patients supplemented with vitamin D2. The Liaison RIA does not appear to have this problem and has been shown to compare favorably with LC-MS/MS. As for the detection of circulating 1,25(OH)2D, everyone is still obliged to perform some sort of sample purification prior to RIA or ELISA. It may be possible to adapt the 1,25(OH)2D RIA to a random access format but almost certainly sample purification prior to assay will always be required. Every laboratory that performs these tests should participate in a quality assurance survey such as DEQAS to ensure integrity in their method. As vitamin D status is implicated with more medical conditions such as cancer, immune function, etc., the demand for these measurements will greatly increase and the automated random access formats will probably emerge due to speed and cost. Let us hope that assay accuracy and reliability remain at least as important.