Laboratory: Clinical Biochemistry
Test Name:
VITAMIN D (25-HYDROXY) - (S)
Test Code: VD25
Clinical Information:
Screening for vitamin D deficiency in healthy individuals is not recommended. 25-OH vitamin D should only be ordered in the following clinical conditions:
 
1.         Metabolic bone disease (recurrent fractures, rickets, osteomalacia, osteopenia, osteoporosis).
2.         Abnormal blood calcium, magnesium, or phosphate concentrations.
3.         Parathyroid disease
4.         Malabsorption syndrome (celiacs disease, cystic fibrosis, small bowel      surgery, medications that interfere with vitamin D absorption such as cholestyramine, orlistat, etc).
5.         Anticonvulsant agents.
6.         Chronic renal disease.
7.         Chronic liver disease.
8.         Intake of high doses of vitamin D combined with symptoms suggestive of hypervitaminosis D
No special patient preparation required.
Collection Devices:
Serum GEL tube is not acceptable. Lithium Heparin No Gel tube is acceptable.
Specimen Required:


Serum: 1.0 mL
Pediatric Serum: 0.25 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 1.0 mL
Pediatric : minimum 0.25 mL

Store and ship serum frozen.
Spin down and separate serum within 1 hour of collection.
Requisition:
Reference Values:
Result                   Interpretation
=>250                   Potentially Harmful
150-249                High
50-149                  Optimal
30-49                    Mild to Moderate Deficiency
<30                       Deficiency
 
(ng/mL x 2.496 = nmol/L)
Availability:
Within 2 Weeks
See Also:
More Information:
Spin down and separate serum. Store and ship serum frozen.
 
References:
 
1) Ross CA, Taylor CL, Yaktine AL, Valle HB Del, eds. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academies Press; 2011.
2)  Chapuy, MC et al.  Osteoporos Int 2002 Mar;13(3):257-64
3)  Bischoff-Ferrari HA  Osteoporos Int 2007 Apr;18(4);401-7
4)  Bischoff-Ferrari HA, et al.  Am J Clin Nutr 2004 Sep;80(3):752-8
5)  Heaney RP  Am J Clin Nutr 2004 Dec;80(6 Suppl):1706S-9S