Hydroxyvitamin D assays: An historical perspective from DEQAS

G D Carter; J Berry; R Durazo-Arvizu; E Gunter; G Jones; J Jones; H L J Makin; P Pattni; C T Sempos; P Twomey; E L Williams; S A Wise

doi:10.1016/j.jsbmb.2017.07.018

Hydroxyvitamin D assays: An historical perspective from DEQAS

J Steroid Biochem Mol Biol. 2018 Mar:177:30-35. doi: 10.1016/j.jsbmb.2017.07.018. Epub 2017 Jul 20.

Authors

G D Carter¹, J Berry², R Durazo-Arvizu², E Gunter², G Jones², J Jones³, H L J Makin², P Pattni³, C T Sempos⁴, P Twomey², E L Williams³, S A Wise⁵

Affiliations

¹ Imperial College Healthcare NHS Trust, Clinical Biochemistry Department, Charing Cross Hospital, London W6 8RF, UK. Electronic address: b.carter1@which.net.
² DEQAS Advisory Panel, Charing Cross Hospital, London W6 8RF, UK.
³ Imperial College Healthcare NHS Trust, Clinical Biochemistry Department, Charing Cross Hospital, London W6 8RF, UK.
⁴ DEQAS Advisory Panel, Charing Cross Hospital, London W6 8RF, UK; National Institutes of Health (NIH) Office of Dietary Supplements (ODS), Bethesda, MD 20892-7517, USA.
⁵ National Institutes of Health (NIH) Office of Dietary Supplements (ODS), Bethesda, MD 20892-7517, USA.

PMID: 28734989
DOI: 10.1016/j.jsbmb.2017.07.018

Abstract

Recent years have seen a substantial increase in demand for 25-hydroxyvitamin D (25-OHD) assays. DEQAS (the Vitamin D External Quality Assessment Scheme) has been monitoring the performance of these assays since 1989. The first DEQAS distribution was in June 1989 and results were submitted by 13 laboratories in the UK, two of which used HPLC/UV; the rest used ligand binding assays with a tritium tracer. Inter-laboratory CVs (ALTM) ranged from 29.3% (42.7nmol/L) to 53.7% (20.0nmol/L). Currently the scheme has participants in 56 countries using 30 methods or variants of methods. In January 2017, 918 participants returned results and inter-laboratory CVs (ALTM) ranged from 10.3% (73.1nmol/L) to 15.3% (29.4nmol/L). Over the last 27 years, there have been a number of significant milestones in assay development. The first major advance was the development of an iodinated 25-OHD tracer by Hollis and Napoli in 1992, subsequently used in an RIA kit marketed by DiaSorin. This and other commercial radioimmunoassays that followed brought 25-OHD assays within reach of many more non-specialist routine laboratories. With the introduction of fully automated non-isotopic assays without solvent extraction, measurement of 25-OHD became available to any clinical chemistry laboratory with an appropriate analytical platform. However, as the limitations of these non-extraction assays became apparent more laboratories started using LC-MS/MS methodology. Meanwhile the variable accuracy of 25-OHD methods has been addressed by the Vitamin D Standardization Program (VDSP) which encourages manufacturers to produce methods traceable to the reference measurement procedures (RMPs) of NIST, University of Ghent and the Centers for Disease Control and Prevention (CDC). DEQAS changed to an accuracy-based scheme in 2013 and now assesses assay accuracy against the NIST RMP. This review will use DEQAS results and statistics to chart the historical development in 25-OHD assay technology and highlight some of the problems encountered in obtaining reliable results for this most challenging of analytes.

Keywords: Assays; DEQAS; History; Hydroxyvitamin D; Performance.

Publication types

Review

MeSH terms

Biological Assay / standards
Biological Assay / trends*
Humans
Vitamin D / analogs & derivatives*
Vitamin D / blood
Vitamins / blood*

Substances

Vitamins
Vitamin D
25-hydroxyvitamin D