Multicenter comparison of seven 25OH vitamin D automated immunoassays

• Main Authors: Lippi Giuseppe, Luca Salvagno Gian, Fortunato Antonio, Dipalo Mariella, Aloe Rosalia, da Rin Giorgio, Giavarina Davide
• Format: Article
• Language: English
• Published: Society of Medical Biochemists of Serbia, Belgrade 2015-01-01
• Series: Journal of Medical Biochemistry
• Subjects: vitamin d; 25oh-d; immunoassays; standardization; method comparison
• Online Access: https://scindeks-clanci.ceon.rs/data/pdf/1452-8258/2015/1452-82581503344L.pdf
• ISSN: 1452-8258; 1452-8266

Background: The measurement of 25OH vitamin D continues to grow in clinical laboratories. The aim of this multicenter study was to compare the results of seven automated commercial immunoassays with a reference HPLC technique. Methods: One hundred and twenty consecutive outpatient serum samples were centrifuged, divided in aliquots, frozen and shipped to the participating laboratories. 25OH Vitamin D was measured with a reference HPLC system and with seven automated commercial immunoassays (Roche Cobas E601, Beckman Coulter Unicel DXI 800, Ortho Vitros ES, DiaSorin Liaison, Siemens Advia Centaur, Abbott Architect i System and IDS iSYS). Results: Compared to the reference method, the regression coefficients ranged from 0.923 to 0.961 (all p< 0.001). The slope of Deming fit ranged from 0.95 to 1.06, whereas the intercept was comprised between -15.2 and 9.2 nmol/L. The bias from the reference HPLC technique varied from -14.5 to 8.7 nmol/L. The minimum performance goal for bias was slightly exceeded by only one immunoassay. The agreement between HPLC and the different immunoassays at 50 nmol/L 25OH Vitamin D varied between 0.61 and 0.85 (all p< 0.001). The percentage of samples below this cut-off was significantly different with only one immunoassay. Conclusions: The excellent correlation with the reference HPLC technique attests that all seven automated immunoassays may be reliably used for routine assessment of 25OH-D in clinical laboratories. The significant bias among the different methods seems mostly attributable to the lack of standardization and calls for additional efforts for improving harmonization of 25OH-D immunoassays.