A novel, fully-automated, chemiluminescent assay for the detection of 1,25-dihydroxyvitamin D in biological samples.

Background: 1,25-Dihydroxyvitamin D (1,25-(OH)D), the hormonal form of vitamin D, is difficult to measure because of its low circulating levels (pg/mL), and similarity to more abundant metabolites. Here a fully-automated chemiluminescent assay that accurately and precisely measures 1,25-(OH)D is described.

Method: The novel 1,25-(OH)D assay was conceived based on four pillars: (1) the VDR's ligand binding domain (LBD) as a capture molecule; (2) reaction conditions wherein 1,25-(OH)D favors binding to LBD vs.