Critically ill need vitamin D – how much and which test to use is TBD – Nov 2014

Vitamin D status in critically ill patients: back to basics!

Critical Care 2014, 18:611 doi:10.1186/s13054-014-0611-0
Anne-Françoise Rousseau1 Anne-Françoise Rousseau afrousseau at chu.ulg.ac.be and Etienne Cavalier2
1 Burn Centre and General Intensive Care Department, University of Liège, University Hospital, Sart-Tilman, Liège, B-4000, Belgium
2 Clinical Chemistry Department, University of Liège, University Hospital, Sart-Tilman, Liège, B-4000, Belgium

Letter
The problem of vitamin D deficiency during intensive care requires a number of clarifications. Initially, it is essential to focus on the fundamentals of vitamin D status assessment. Total 25-hydroxyvitamin D (25OH-D) is currently considered as the best indicator of vitamin D status. Due to practical reasons (less knowledge needed, higher throughput), immunoassays are generally preferred to measure serum 25OH-D levels. In the critical care context, however, they may be biased due to matrix effects [1]. During the acute phase of critical care, these assays should then be abandoned in favor of liquid chromatography-tandem mass spectrometry. Moreover, standardization of vitamin D assays is crucial: such a process is ongoing worldwide but, to date, is still incomplete. It is important to note that both points are rarely considered in the published studies related to vitamin D in critically ill patients: the data may thus be interpreted with caution.

The bioavailable and free fraction of 25OH-D are attractive complementary markers of vitamin D status; however, progress is needed before establishing their evidence [2]. We need an accurate assay rather than formulas to measure free and bioavailable concentrations. We also need to determine normal or optimal ranges and to investigate their clinical impact. In the future, it seems important to consider these analytical prerequisites when studying vitamin D in critically ill patients. Meanwhile, these patients should benefit from the potential beneficial effects of vitamin D. Cholecalciferol is, in fact, a cheap medication with a wide therapeutic window. We believe that the critically ill should be supplemented with vitamin D as they are clearly at risk of deficiency. Meanwhile, for specific protocols, intensivists should at least follow the Endocrine Society guidelines [3],[4].

References

1. Rousseau AF, Damas P, Janssens M, Kalin S, Ledoux D, Le Goff C, Gadisseur R, Delanaye P, Cavalier E:
   Critical care and vitamin D status assessment: what about immunoassays and calculated free 25OH-D?
2. Clin Chim Acta 2014, 437:43-47. PubMed Abstract | Publisher Full Text OpenURL
3. De Pascale G, Quraishi SA: Vitamin D status in critically ill patients: the evidence is now available!
4. Crit Care 2014, 18:449. PubMed Abstract | BioMed Central Full Text OpenURL
5. Heaney RP, Holick MF: Why the IOM recommendations for vitamin D are deficient.
6. J Bone Miner Res 2011, 26:455-457. PubMed Abstract | Publisher Full Text OpenURL
7. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM:
   Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline.
8. J Clin Endocrinol Metab 2011, 96:1911-1930. PubMed Abstract | Publisher Full Text OpenURL

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