Comparison of Automated 25-OH Vitamin D Immunoassays with Liquid Chromatography Isotope Dilution Tandem Mass Spectrometry

Abstract

Comparing two fully automated 25-OH-D immunoassays with a validated liquid chromatography isotope dilution tandem mass spectrometry (LC-IDMS/MS) method in human serum samples. 180 samples were analyzed with the Liaison TOTAL Vitamin D, the IDS-iSYS 25-Hydroxy Vitamin D, and a validated LC-IDMS/MS 25-OH D method. The Liaison method mean +/- standard deviation (SD) was 64.3 +/- 23.5 nmol/L; the IDS-iSYS 70.1 +/- 27.0 nmol/L, and the LC-IDMS/MS 68.9 +/- 24.6 nmol/L. The correlation coefficient (r) between the Liaison and LC-IDMS/MS was 0.723, and the r between the IDS-iSYS and LC-IDMS/MS was 0.799. When the samples were grouped by females and males, the r between the Liaison and LC-IDMS/MS was 0.680 and 0.846, being 0.781 and 0.863 between the IDS-iSYS and LC-IDMS/MS, respectively. With the Passing-Bablok analysis, only the IDS-iSYS gave equivalent results to LC-IDMS/MS. The automated 25-OH-D immunoassays were in clinically good overall agreement with the LC-IDMS/MS method.