Critical care and vitamin D status assessment: what about immunoassays and calculated free 25OH-D?

Anne-Françoise Rousseau; Pierre Damas; Marc Janssens; Saban Kalin; Didier Ledoux; Caroline Le Goff; Romy Gadisseur; Pierre Delanaye; Etienne Cavalier

doi:10.1016/j.cca.2014.07.007

Critical care and vitamin D status assessment: what about immunoassays and calculated free 25OH-D?

Clin Chim Acta. 2014 Nov 1:437:43-7. doi: 10.1016/j.cca.2014.07.007. Epub 2014 Jul 11.

Authors

Anne-Françoise Rousseau¹, Pierre Damas², Marc Janssens³, Saban Kalin³, Didier Ledoux², Caroline Le Goff⁴, Romy Gadisseur⁴, Pierre Delanaye⁵, Etienne Cavalier⁴

Affiliations

¹ Burn Centre and General Intensive Care Department, University of Liège, University Hospital, Sart-Tilman, Liège, Belgium. Electronic address: afrousseau@chu.ulg.ac.be.
² Burn Centre and General Intensive Care Department, University of Liège, University Hospital, Sart-Tilman, Liège, Belgium.
³ Anesthesiology Department, University of Liège, University Hospital, Sart-Tilman, Liège, Belgium.
⁴ Clinical Chemistry Department, University of Liège, University Hospital, Sart-Tilman, Liège, Belgium.
⁵ Nephrology Department, University of Liège, University Hospital, Sart-Tilman, Liège, Belgium.

PMID: 25020235
DOI: 10.1016/j.cca.2014.07.007

Abstract

Background: Interpretation of 25OH-D measurement during critical care (CC) may be problematic due to variations of binding protein concentrations (albumin, ALB, and vitamin D binding protein, VDBP). Determination of free 25OH-D concentration may thus be relevant in CC patients. The aim of this observational study was to evaluate effects of an acute hemodilution on vitamin D (VD) status.

Methods: Blood samples were obtained before (T1) and after a crystalloid load (T2) administered at anesthesia induction for minor surgery. 25OH-D was measured with LC-MS/MS and with 3 immunoassays (IA): DiaSorin Liaison, IDS iSYS and bioMérieux Vidas. VDBP was measured with the R&D Elisa and ALB on Cobas. Free 25OH-D was calculated using published formula. Accuracy of each 25OH-D IA was calculated as the percentage of IA values within 20% of their respective LC-MS/MS values. Performances of the three AI were compared with LC-MC/MS using Bland-Altman analysis.

Results: Twenty adults were included. Compared to T1 values, VDBP, ALB and LC-MS/MS values decreased in parallel by a mean of 23% at T2. IA values decreased less significantly (12, 14 and 15% for Liaison, iSYS and Vidas, respectively). IA-based calculated free 25OH-D significantly increased after dilution, while LC-MS/MS-based free values remained stable. At T1 and T2, bias were demonstrable for all IA. After hemodilution, bias would lead to overestimation for the three IA. Accuracy of IA decreased after dilution.

Conclusions: Due to matrix effects, compared to LC-MS/MS, IA results were impacted by hemodilution. In CC patients, LC-MS/MS seems to be the best option to measure 25OH-D. Specific LC-MS/MS method should be developed to measure free 25OH-D.

Keywords: Critical care; Free 25-hydroxyvitamin D; Hemodilution; Immunoassay; Vitamin D.

Publication types

Observational Study

MeSH terms

Adult
Aged
Biomarkers / blood
Calcifediol / blood*
Chromatography, Liquid / methods
Critical Care / methods*
Critical Care / standards*
Critical Illness / therapy*
Female
Humans
Immunoassay / methods
Male
Mass Spectrometry / methods
Middle Aged
Vitamin D / blood
Vitamin D Deficiency / blood*
Vitamin D Deficiency / diagnosis*
Young Adult

Substances

Biomarkers
Vitamin D
Calcifediol