Poster 19 biochimie

Evaluation of a 1,25-Dihydroxy Vitamin D Assay on the IDS-iSYS Automated System S. Bergmann a , M.J. Gardner b , C.M. Roffe b , C.J. Fox b , D Laurie b , Z. Seres b and M.L. Garrity b a TUD UKD Institute of Clinical Chemistry and Laboratory Medicine, Dresden, Germany and b Immunodiagnostic Systems (IDS) Ltd, Boldon. U.K. 2011 Biochemistry Biochemistry Poster 19

1,25-dihydroxyvitamin D (1,25D) is one of the major regulators of calcium metabolism. It stimulates intestinal calcium absorption, increases bone resorption and inhibits parathyroid hormone (PTH) production by direct action on the parathyroid glands.
Measurement of 1,25D is used in conjunction with 25-hydroxyvitamin D (25D) and PTH in the differential diagnosis of various bone diseases. 1,25D production is impaired in end stage renal disease (ESRD) and levels are often low in these patients. As such 1,25D is an obvious addition to the IDS–iSYS calcium metabolism and bone turnover markers panels consisting of 25-Hydroxy Vitamin D, Intact PTH, Intact PINP, CTX-I (CrossLaps ® ), Ostase ® BAP and N-MID ® Osteocalcin.
Only a small proportion of 25D is further hydroxylated in the kidney to the active calciotropic hormone. Therefore levels of 1,25D in serum and plasma are generally low (pg/mL) compared to 25D (ng/mL). Added to this 1,25D is attached to vitamin D binding protein and is ready soluble in the lipid phase of samples. All this makes development of 1,25D assays technically challenging. Presently, there are no semi or fully automated 1,25D assays available. The IDS-iSYS 1,25 Dihydroxy Vitamin D from IDS is the first semi-automated assay of the market.
Reagents and methods have been further advanced since feasibility trials on preliminary reagents (ECTS, poster PP165-T 2011). The aim was to evaluate trial reagents both at IDS and at an external site in Dresden, Germany. The assay itself employs the well established IDS immunoextraction technology for front end extraction of 1,25D from samples. This is combined with assay reagents specifically developed for use with the fully automated IDS-iSYS system.
Introduction

Patients and Methods

Calibration and Assay Range
During this evaluation, the calibration was performed by using a 7 point calibrator set prepared using a buffer-based matrix. The 1,25D IDS-iSYS assay had an assay range of 3.7 – 400pg/mL and produced comparable curves at both sites.
Patients and Methods Figure 2. Mean Calibration Curve of IDS-iSYS 1,25D Assay

Results

The combination of immunoextraction and the IDS-iSYS system will allow laboratories to analyze much larger number of samples in singlicate within a day. With excellent sensitivity, precision, linearity and good correlation to the current 1,25D RIA method, the IDS-iSYS 1,25-Dihydroxy Vitamin D assay will be a valuable tool in clinical laboratories for the accurate measurement of 1,25D in serum, EDTA and heparinised plasma.
Summary

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Poster 19 biochimie

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