Laboratory: Clinical Biochemistry
Test Name:
VITAMIN D (1,25-DIHYDROXY) - (S)
Test Code: D125
Clinical Information:
THIS TEST IS ONLY AVAILABLE TO ENDOCRINOLOGIST AND NEPHROLOGIST. ALL OTHER REQUESTS MUST BE APPROVED BY A CLINICAL BIOCHEMIST USING THE DESIGNATED TEST APPROVAL FORM.
 
Screening for vitamin D deficiency in healthy individuals is not recommended.
 
This test is not appropriate for diagnosing vitamin D deficiency or insufficiency. 1,25-OH vitamin D should only be ordered in the following clinical conditions:
 
1.         Clinical evidence of vitamin D deficiency due to hereditary deficiency of renal 1-alpha hydroxylase or end-organ resistance to 1,25-dihydroxy vitamin D.
2.         Hypercalcemia or renal failure in addition to Vitamin D, 25-Hydroxy testing.

No special patient preparation required.
 
Collection Devices:
Preferred Device:
Alternate Device:
1 - Microtainer(s) - Plain Serum, NO GEL (0.5 mL) to fill line  - Alternate Device
Serum GEL tube is not acceptable. Lithium Heparin No Gel tube is acceptable. 
Specimen Required:
Serum: 2.0 mL
Pediatric Serum: 1.0 mL


Serum: 2.0 mL

Note that minimum volume does not allow for repeat analysis.
Referral:

Serum collected WITHOUT separator gel in aliquot tube shipped in on ice.
Adult: minimum 2.0 mL
Pediatric : minimum 1.0 mL

Spin down and separate serum. Store and ship serum frozen.
Requisition:
Reference Values:
Reference values will be given with report.
Complete details of the reference values are available at  In-Common Laboratories Reference Values
http://www.hicl.on.ca/search_tcna.asp?TCString=125VITD

 
Availability:
Within 2 Weeks
This test is a referral to In-Common Labs, Ontario. All requests from physicians other than Endocrinologist & Nephrologist must be approved by a Clinical Biochemist before lab send out.
See Also:
More Information:
Serum collected WITHOUT separator gel in aliquot tube shipped in on ice. Store and ship serum frozen.
 
Spin down and separate serum.
 
References:
 
1.         Choosing Wisely: Don’t routinely measure 1,25-dihydroxyvitamin D unless the patient has hypercalcemia or decreased kidney function. http://www.choosingwisely.org/clinician-lists/endocrine-society-vitamin-d-testing/
2.         Bringhurst FR, Demay MB, Kronenberg HM: Vitamin D (calciferols): metabolism of vitamin D. In Williams Textbook of Endocrinology. Ninth edition. Edited by JD Wilson, DW Foster, HM Kronenberg, PR Larsen. Philadelphia, WB Saunders Company, 1998, pp 1166-1169.
3.         Bikle D, Adams J, Christakos S. Primer on the metabolic bone diseases and disorders of mineral metabolism. Washington: American Society for Bone and Mineral Research. c2008.Chapter 28, Vitamin D: production, metabolism, mechanism of action, and clinical requirements. p. 141-9.
4.         Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357:266-81.
5.         Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM; Endocrine Society. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011 Jul;96(7):1911-30.