Current 25-hydroxyvitamin D assays: Do they pass the test?

• Published in: Clinica chimica acta Vol. 413; no. 13-14; pp. 1127 - 1134
• Main Authors: Ong, Lizhen, Saw, Sharon, Sahabdeen, Noorulhijjah Bte, Tey, Kiat Teng, Ho, Chung Shun, Sethi, Sunil Kumar
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 11.07.2012
• Subjects: 25OHD testing; Accuracy; Chromatography, Liquid; Correlation; Humans; Immunoassay; Luminescent Measurements - standards; Precision; Quality Control; Radioimmunoassay; Reproducibility of Results; Sensitivity and Specificity; Tandem Mass Spectrometry; Uncertainty; Vitamin D; Vitamin D - analogs & derivatives; Vitamin D - blood; Vitamin D Deficiency - blood; Vitamin D Deficiency - diagnosis; Correlation; Accuracy; 25OHD testing; Vitamin D; Precision
• ISSN: 0009-8981; 1873-3492
• DOI: 10.1016/j.cca.2012.03.009

Vitamin D testing is becoming increasingly important with recent research demonstrating a correlation between vitamin D insufficiency and metabolic diseases, immunodeficiencies and other diseases. However, existing 25-hydroxyvitamin D (25OHD) assays lack comparability to the candidate reference method, causing difficulties in diagnosis and monitoring of vitamin D deficiency. We looked at the accuracy of 3 automated assays (Roche Diagnostics Elecsys® Total 25OHD assay, Abbott Architect® Total vitamin D assay, Advia Centaur® vitamin D Total assay) and Diasorin® Radioimmunoassay (RIA) compared to a routine laboratory Liquid Chromatography–Tandem Mass Spectrometry (LC–MS/MS). The correlation based on Passing Bablok regression was good with the slopes between 0.95 and 1.31 and the intercepts between −3.24 and 3.68. However, a significant positive bias was observed using the Abbott Architect and the Diasorin RIA. Using published analytical goals of coefficient of variation (CV) <10% and bias <5%, most methods did not meet these criteria. Using measurement of uncertainty of 9%, most methods were able to meet criteria using quality control materials but not patient samples. Inadequacies of these assay performances are contributed by differences in method of extraction of vitamin D from vitamin D binding protein, cross-reactivities to 25OHD2, 25OHD3 and other vitamin D metabolites, matrix interferences and a lack of standardization. ► Five 25-hydroxyvitamin D (25OHD) assays were compared. ► Four 25OHD assays were evaluated using accuracy and precision data. ► The imprecision of quality control samples for the immunoassays was all below 10%. ► The imprecision of pooled serum samples for immunoassays was between 2.7% and 22.8%. ► Based on stringent analytical goals, most 25OHD assays did not meet the standards.