The anomalous behaviour of exogenous 25-hydroxyvitamin D in competitive binding assays

G. D. Carter, J. C. Jones, J. L. Berry

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The Vitamin D International External Quality Assessment Scheme (DEQAS) was established in 1989 to monitor the performance of assays for 25-hydroxyvitamin D (25-OHD) and 1,25-dihydroxyvitamin D (I,25(OH) 2D). This is achieved through the quarterly distribution of five samples of human serum. Results are used to calculate an All-Laboratory Trimmed Mean and a Method Mean for each of the methods used by participants. In July 2005, participants were asked to assay serum to which 50.9 nmol of either 25-OHD 3 or 25-OHD 2 had been added as ethanolic solutions. The final concentration of ethanol in the serum was 0.7%. The distribution also included a sample of the original serum (OS) containing 0.7% pure ethanol. The percentage recoveries of exogenous 25-OHD 3 (R1) and 25-OHD 2 (R2) were calculated for each method. Results (OS nM, R1 and R2) were as follows: DiaSorin RIA (n = 53); 39.2, 82.1%, 83.3%, DiaSorin Liason (n = 16); 36.8, 81.4%, 88.6%, IDS RIA (n = 21); 36.4, 54.2%, 29.1%, IDS OCTEIA (n = 16); 47.3, 78.8%, 56.4%, Nichols Advantage (n = 21); 58.9, 46.4%, 43.2%, HPLC (n = 9); 42.6, 112.2%, 97.1%, LC-MS (n = 4); 34.0, 111.5%, 118.1%. The IDS RIA and Nichols assays gave unexpectedly low recoveries. This does not appear to be a calibration problem or the effect of ethanol. © 2006 Elsevier Ltd. All rights reserved.
    Original languageEnglish
    Pages (from-to)480-482
    Number of pages2
    JournalJournal of Steroid Biochemistry and Molecular Biology
    Volume103
    Issue number3-5
    DOIs
    Publication statusPublished - Mar 2007

    Keywords

    • 25-Hydroxyvitamin D
    • DEQAS
    • Recovery

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