Change in Instrumentation & Methodology: Vitamin D, 25 OH

Effective January 9, 2023, Clinical Pathology Laboratories (CPL) is pleased to announce a change in the method and analytic platform for Vitamin D, 25 OH (Hydroxyvitamin D). This change provides increased efficiency, optimized handling of low-volume specimens, and improved turnaround time and test capacity.

The new methodology is competitive electrochemiluminescence binding assay with cross-reactivity to Dihydroxyvitamin D blocked by a specific monoclonal antibody. CPL has extensively validated the method including correlation with the laboratory’s Hydroxyvitamin D by liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. In addition, the new method has been standardized against and is traceable to the National Institute of Standards and Technology Standard Reference Material 2972.

The change in instrumentation and methodology will not affect the current interpretive ranges used by CPL.

The new methodology will allow for an analytical measuring range of 6 - 120 ng/mL without dilution, and clinical reporting range up to 240 ng/mL with an automatic dilution by the instrumentation. The current methodology has an analytical measuring range of 4 - 150 ng/mL. 99.9 % of results fall within the 6 - 240 ng/mL range.

Vitamin D is a fat-soluble hormone precursor that is biologically inert and must undergo two successive hydroxylations in the liver and kidney to form the 1,25-Dihydroxyvitamin D form that affects calcium metabolism and bone mineralization. The determination of the vitamin D sufficiency status is performed using a 25-Hydroxyvitamin D (Vitamin D, 25 OH) assay while 1,25-Dihydroxyvitamin D assessment is primarily indicated for evaluation of hypercalcemia and for assessing patients with renal failure.

The two main forms of Vitamin D are D2 and D3. Vitamin D2 cannot be synthesized by the human body and must be taken in with food or supplements. In contrast, Vitamin D3 is produced in the skin by exposure to sunlight. Vitamin D deficiency can lead to bone-malformation (rickets), underutilization of dietary calcium, muscle weakness, and reduced bone mass.