Analytical and clinical validation of the 25 OH vitamin D assay for the LIAISON automated analyzer.

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 LIAISON 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 LIAISON 25 OH Vitamin D assay is a rapid, accurate, and precise tool for the measurement of 25 OH vitamin D.