Vitamin D: marker, measurand & measurement
Niek F Dirks1,2, Etienne Cavalier3, Annemieke C Heijboer4,5,6,7
1Atalmedial Diagnostics Centre, Spaarne Gasthuis, Haarlem, The Netherlands.
Endocrine Connections
|January 23, 2023
Summary
Accurate vitamin D status assessment requires understanding vitamin D metabolite measurements. Automated assays may misinterpret results for some patients, especially those using vitamin D2, making liquid chromatography-tandem mass spectrometry a more reliable option.
Area of Science:
- Clinical Chemistry
- Endocrinology
- Nutritional Science
Background:
- Vitamin D metabolites are crucial for assessing vitamin D status and diagnosing calcium homeostasis disorders.
- Laboratories commonly measure total 25-hydroxyvitamin D (25(OH)D), with some offering separate measurements of 25(OH)D2 and 25(OH)D3, and other metabolites like 1,25-dihydroxyvitamin D and 24,25-dihydroxyvitamin D.
Purpose of the Study:
- To provide an updated overview of key vitamin D metabolism markers.
- To define intended measurands for vitamin D assays.
- To discuss the pros and cons of automated assays versus liquid chromatography-tandem mass spectrometry (LC-MS/MS).
Main Methods:
- Review of current literature on vitamin D metabolite assays.
- Comparative analysis of automated immunoassays and LC-MS/MS techniques.
- Discussion of assay limitations and interpretation pitfalls.
Main Results:
- Automated assays may not accurately measure 25(OH)D in all patient populations, particularly those supplemented with vitamin D2.
- LC-MS/MS offers a more reliable measurement of 25(OH)D, especially when properly developed and standardized.
- Understanding assay-specific limitations is vital for accurate interpretation of vitamin D status.
Conclusions:
- Automated assays have limitations in accurately quantifying 25(OH)D for certain patient groups, including those using vitamin D2.
- LC-MS/MS provides a more dependable method for measuring 25(OH)D when validated and standardized.
- Clinical laboratories must be aware of assay pitfalls to ensure accurate patient diagnosis and management of vitamin D status.
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