Recertification of 25-hydroxyvitamin D standards by Isotope Pattern Deconvolution (IPD)

Vitamin D (VTD) is an important prohormone widely known since its deficiency is directly related to development of rickets in children and osteoporosis in adults. Furthermore, recent studies have demonstrated that vitamin D has also an important role in non-skeletal conditions such as autoimmune diseases, cardiovascular diseases and cancer, among others. This vitamin can be found in two main forms: vitamin D2 and vitamin D3. The metabolism of both forms of vitamin D are subjected to a first hydroxylation in the liver to form 25-hydroxyvitamin D (25(OH)D) and then to a second one in the kidney to form 1,25-dihydroxyvitamin D (1,25(OH)2D), the active form of vitamin D. Nevertheless, the measurement of 25(OH)D in serum samples is preferred test for the assessment of vitamin D status over the 1,25(OH)2D. There are two main reasons for this choice: the longer lifetime (3 weeks versus 4 h) and its higher concentration levels (ng/mL versus pg/mL)[2].
Over the last years, a dramatic rise in vitamin D testing (as 25(OH)D) has been observed, due to two main reasons: the increased number of patients with VTD deficiency and the increase of the role of VTD as a biomarker related to several diseases.
In this work we propose a recertification approach for 25(OH)D2/D3 solvent standards based on Isotope Pattern Deconvolution (IPD) using NIST SRM 2972 as reference material. This approach could help to meet the requirements for external standardization criteria using in-house calibration curves.