Standardization of misleading immunoassay based 25-hydroxyvitamin D levels with liquid chromatography tandem-mass spectrometry in a large cohort study

• Published in: PloS one 2012-11, Vol.7 (11), p.e48774-e48774
• Main Authors: Schöttker, Ben, Jansen, Eugène H J M, Haug, Ulrike, Schomburg, Lutz, Köhrle, Josef, Brenner, Hermann
• Format: Article
• Language: English
• Subjects: 25-Hydroxyvitamin D; Aged; Analysis; Automation; Cancer; Chemistry; Chromatography; Chromatography, Liquid - methods; Cohort analysis; Cohort Studies; Epidemiology; Female; Humans; Immunoassay; Immunoassay - methods; Immunoassay - standards; Immunoassays; Laboratories; Liquid chromatography; Male; Mass spectrometry; Mass spectroscopy; Mathematical models; Medical research; Medicine; Men; Mens health; Methods; Middle Aged; Population studies; Reproducibility of Results; Scientific imaging; Spectroscopy; Standardization; Tandem Mass Spectrometry - methods; Vitamin D; Vitamin D - analogs & derivatives; Vitamin D - blood; Vitamin D Deficiency - blood; Vitamin D Deficiency - diagnosis; Vitamin deficiency; Womens health
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0048774

The interest in vitamin D measurement has strongly increased in recent years. The best indicator for circulating vitamin D levels is 25-hydroxy-vitamin D (25(OH)D) which is often measured by different immunoassays. We demonstrate problems in comparability of measures by different immunoassays and the need for standardization in the context of a large population-based cohort study. 25(OH)D was measured with the immunoassays Diasorin Liaison in 2006 in 5,386 women and in the context of another project with IDS-iSYS in 4,199 men in 2009-2010 (when the Diasorin Liaison was no longer available in the version utilized in 2006). Standardization was performed by re-measuring of 25(OH)D levels in 97 men and 97 women with liquid chromatography tandem-mass spectrometry (LC-MS/MS) to obtain linear regression conversion equations. Applying a 30 nmol/L cut-off value for vitamin D deficiency would have resulted in 48.3% of women and 12.1% of men with vitamin D deficiency ahead of standardization. The large gender difference was strongly attenuated after standardization of the assays with only 15.7% of women and 14.3% of men with vitamin D deficiency. Standardization on average increased the 25(OH)D levels by 10.3 nmol/L in women and decreased 25(OH)D levels by 2.9 nmol/L in men. The standardization with LC-MS/MS revealed that much of the observed gender difference was only assay-driven and the extremely high proportion of 48.3% vitamin D deficient women proved to be an exaggeration of the old version of the Diasorin-Liaison immunoassay. Standardization of 25(OH)D immunoassay results by LC-MS/MS is recommended to improve their accuracy and comparability, provided the LC-MS/MS method itself is adequately validated and standardized.