Analytical and clinical validation of the 25 OH vitamin D assay for the LIAISONR automated analyzer Diana L. Ersfeld a , D. Sudhaker Rao b , Jean-Jacques Body c , James L. Sackrison, Jr. a , Andrew B. Miller a , Nayana Parikh b , Tar Lisha Eskridge b , Amy Polinske a , Gregory T. Olson a , Gordon D. MacFarlane a, * a Research and Development, DiaSorin Inc., Stillwater, MN 55082, USA b Henry Ford Hospital, Detroit, MI 48202, USA c Institut Jules Bordet, Brussels, Belgium Received 5 March 2004; received in revised form 16 June 2004; accepted 17 June 2004 Abstract Objective: Methods to assess serum 25 OH vitamin D have improved in accuracy, precision, and ease of use. We describe the analytical and clinical validation of an automated, antibody- and microparticle-based, chemiluminescent immunoassay method for the determination of 25 OH vitamin D. Design and methods: The LIAISONR 25 OH Vitamin D assay is a rapid automated method with first results available in 40 min, and a subsequent throughput of 180 samples per hour. Assay performance characteristics of precision and recovery were determined according to the National Committee for Clinical Laboratory Standards (NCCLS) protocols. Analytical and functional sensitivity were determined according to standard protocols. Samples for method comparison studies were obtained from routine clinical samples submitted for 25 OH Vitamin D determination or from apparently healthy normal volunteers. Results: The detection limit for this assay was <2.0 nmol/L across three lots of materials. Functional sensitivity (inter-assay imprecision <20%) was 17.5 nmol/L. Total imprecision (CV) was <15% at 42.5– 137.5 nmol/L. Mean (SD) recovery was 101% (13%). The assay was linear on dilution. Comparison with radioimmunoassay (RIA) yielded acceptable correlation (r = 0.88) and clinical equivalence in the range from 37.5 to 150 nmol/L. Conclusions: The LIAISONR 25 OH Vitamin D assay is a rapid, accurate, and precise tool for the measurement of 25 OH vitamin D. D 2004 The Canadian Society of Clinical Chemists. All rights reserved. Keywords: 25 OH Vitamin D; Chemiluminescent assay; LIAISONR analyzer; Osteomalacia; Hypovitaminosis D Introduction Low vitamin D status is being associated with a growing number of diseases. Severe vitamin D deficiency has long been associated with rickets in children and osteomalacia in adults [1,2]. Serum concentrations of 25 OH vitamin D of less than 40–50 nmol/l (16–20 Ag/l) can lead to secondary hyperparathyroidism and its deleterious consequences on bone mass over the long term [3,4]. Serum 25 OH Vitamin D concentrations less than 80 nmol/L have been shown to impair absorption of intestinal calcium [5]. Vitamin D defi- ciency has been associated with disturbed muscle metabolism [6], particularly impaired intracellular calcium metabolism [7]. High circulating concentrations of NT-proANP, a marker of the severity of congestive heart failure, has been associated with low circulating 25 OH vitamin D concentrations [8]. In addition, vitamin D status has been linked to prostate, breast, and colon cancer [9–11]. Currently, the circulating 25 OH vitamin D concentration is the best available index of vitamin D nutritional status [12,13]. Therefore, the measurement of 25 OH vitamin D is becoming increasingly important to the diagnosis and management of numerous diseases. The measurement of 25 OH vitamin D has evolved through several technologies. Several high-performance 0009-9120/$ - see front matter D 2004 The Canadian Society of Clinical Chemists. All rights reserved. doi:10.1016/j.clinbiochem.2004.06.006 Abbreviations: CRF, chronic renal failure; ESRD, end-stage renal disease; NCCLS, National Committee for Clinical Laboratory Standards. * Corresponding author. Research and Development, DiaSorin Inc., 1951 Northwestern Avenue, Stillwater, MN 55082. Fax: +1-651-351-5669. E-mail address: gordon.macfarlane@diasorin.com (G.D. MacFarlane). Clinical Biochemistry 37 (2004) 867 – 874