Esoterix
Test Includes
Total Vitamin D, Vitamin D2, Vitamin D3
Expected Turnaround Time
3 - 6 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Specimen Requirements
Specimen
Serum (preferred) or plasma
Volume
1.0 mL
Minimum Volume
0.5 mL (Note: This volume does not allow for repeat testing.)
Container
Red-top tube, gel-barrier tube, lavender-top (EDTA) tube, or green-top (heparin) tube
Collection
Serum or plasma must be separated from cells within 45 minutes of venipuncture. Submit serum or plasma in a plastic transport tube.
Storage Instructions
Freeze. Stable frozen for 34 months. Stable at room temperature or refrigerated for 7 days.
Test Details
Use
25-Hydroxy vitamin D is used to measure vitamin D status; it includes results for total 25-hydroxy vitamin D2 and 25-hydroxy vitamin D3.
Methodology
High-pressure liquid chromatography/tandem mass spectrometry (HPLC/MS-MS)
Additional Information
The biological function of vitamin D is to maintain normal levels of calcium and phosphorus absorption. 25-Hydroxy vitamin D is the storage form of vitamin D. Vitamin D assists in maintaining bone health by facilitating calcium absorption. Vitamin D deficiency can also cause osteomalacia, which frequently affects elderly patients. Vitamin D from sunshine on the skin or from dietary intake is converted predominantly by the liver into 25-hydroxy vitamin D, which has a long half-life and is stored in the adipose tissue. The metabolically active form of vitamin D, 1,25-di-hydroxy vitamin D, which has a short life, is then synthesized in the kidney as needed from circulating 25-hydroxy vitamin D. The reference interval of greater than 30 ng/mL is a target value established by the Endocrine Society.1
Footnotes
Holick MF, Binkley NC, Bischoff-Ferrare HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: An Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011; 96(7):1911-1930. PubMed 21646368