First 25-hydroxyvitamin D assay for general chemistry analyzers

Abstract

25-Hydroxyvitamin D [25(OH)D], the predominant circulating form of vitamin D, is an accurate indicator of the general vitamin D status of an individual. Because vitamin D deficiencies have been linked to several pathologies (including osteoporosis and rickets), accurate monitoring of 25(OH)D levels is becoming increasingly important in clinical settings. Current 25(OH)D assays are either chromatographic or immunoassay-based assays. These assays include HPLC, liquid chromatography-tandem mass spectrometry (LC-MS/MS), enzyme-immunosorbent, immunochemiluminescence, immunofluorescence and radioimmunoassay. All these assays use heterogeneous formats that require phase separation and special instrumentations. In this article, we present an overview of these assays and introduce the first homogeneous assay of 25(OH)D for use on general chemistry analyzers. A special emphasis is put on the unique challenges posed by the 25(OH)D analyte. These challenges include a low detection limit, the dissociation of the analyte from its serum transporter and the inactivation of various binding proteins without phase separation steps.

Keywords:

• 25-hydroxyvitamin D
• CLIA
• cloned enzyme-donor immunoassay
• colorimetric detection
• EIA
• FIA
• general chemistry analyzer
• RIA
• vitamin D binding protein

Financial & competing interests disclosure

All authors are employees of Diazyme. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Key issues

• 25-Hydroxyvitamin D [25(OH)D] is the accurate indicator of the general vitamin D status of an individual.

• 25(OH)D deficiencies are linked to many diseases.

• 25(OH)D testing has been growing exponentially in the past decade.

• Currently available assays for 25(OH)D are expensive, require special equipment, have low throughput and cannot be run in standard clinical chemistry labs.

• To meet the increasing demand for vitamin D testing, Diazyme developed the first fully automated colorimetric assay for 25(OH)D that runs on general chemistry analyzers.

• The Diazyme assay is poised to transform 25(OH)D into an affordable routine clinical chemistry test.

• Identifying and counteracting the effect of previously unknown 25(OH)D substances is essential to improve the accuracy and the agreement between various 25(OH)D assays.

Notes