Reference intervals for serum 24,25-Dihydroxyvitamin D and the ratio with 25-Hydroxyvitamin established using a newly developed LC-MS/MS method

Tang, Jonathan C. Y. ORCID:, Nicholls, Holly, Piec, Isabelle ORCID:, Washbourne, Christopher J., Dutton, John J., Jackson, Sarah, Greeves, Julie and Fraser, William D. (2017) Reference intervals for serum 24,25-Dihydroxyvitamin D and the ratio with 25-Hydroxyvitamin established using a newly developed LC-MS/MS method. Journal of Nutritional Biochemistry, 46. 21–29. ISSN 0955-2863

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24,25(OH)2D is the product of 25(OH)D catabolism by CYP24A1.The measurement of serum 24,25(OH)2D concentration may serve as an indicator of vitamin D catabolic status and the relative ratio with 25(OH)D can be used to identify patients with inactivating mutations in CYP24A1. We describe a LC-MS/MS method to determine: 1) the relationships between serum 24,25(OH)2D and 25(OH)D; 2) serum reference intervals in healthy individuals; 3) the diagnostic accuracy of 24,25(OH)2D measurement as an indicator for vitamin D status; 4) 24,25(OH)2D cut-off value for clinically significant change between inadequate and sufficient 25(OH)D status. Serum samples of healthy participants (n=1996) from Army recruits and patients (n=294) were analysed. The LC-MS/MS assay satisfied industry standards for method validation. We found a positive, concentration-dependent relationship between serum 24,25(OH)2D and 25(OH)2D concentrations. The 25(OH)D:24,25(OH)2D ratio was significantly higher (p<0.001) at 25(OH)D <50 nmol/L. The reference interval for 25(OH)D:24,25(OH)2D ratio in healthy subjects was 7-23. Measurement of serum 24,25(OH)2D can be used as predictor of vitamin D status, a concentration of >4.2 nmol/L was identified as a diagnostic cut-off for 25(OH)D replete status. One patient sample with an elevated 25(OH)D:24,25(OH)2D ratio of 32 and hypercalcaemia who on genetic testing confirmed to have a biallelic mutation of CYP24A1. Our study demonstrated the feasibility of a combined 24,25(OH)2D and 25(OH)D assessment profile. Our established cut-off value for 24,25(OH)2D and ratio reference ranges can be useful to clinicians in the investigation of patients with an impaired calcium/phosphate metabolism and may point towards the existence of CYP24A1 gene abnormalities.

Item Type: Article
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Pure Connector
Date Deposited: 11 Apr 2017 05:09
Last Modified: 24 Sep 2022 02:19
DOI: 10.1016/j.jnutbio.2017.04.005

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