Order Code: C339
ABN Requirement: No
Synonyms: Vitamin D (Total); 25-Hydroxycalciferol; 25-OH-D; Cholecalciferol Metabolite; Vitamin D; Vit D; Total Vitamin D
Specimen: EDTA Plasma or Serum
Volume: 0.5 mL
Minimum Volume: 0.2 mL
Container: EDTA (Lavender Top tube) or Gel-barrier tube (SST, Tiger Top)
- Draw and gently invert 8 to 10 times.
- Centrifuge for 10 minutes.
- Pre-squeeze transfer pipet bulb and draw off approximately 2/3 of the upper plasma layer.
Note: This ensures that the buffy coat and red cells remain undisturbed.
- Aliquot plasma into labeled transport tube and cap tightly. Discard original tube.
- Store transport tube refrigerated at 2-8°C until ready to ship.
- Collect and label sample according to standard protocols.
- Gently invert tube 5 times immediately after draw. DO NOT SHAKE.
- Allow blood to clot 30 minutes.
- Centrifuge for 10 minutes.
Special Instructions: Minimize sample exposure to direct sunlight.
Transport: Store serum at 2°C to 8°C after collection and ship the same day per packaging instructions provided with the Cleveland HeartLab shipping box.
Ambient (15-25°C): 21 days
Refrigerated (2-8°C): 21 days
Frozen (-20°C): 185 days
Deep frozen (-70°C): 185 days
Causes of Rejection: Specimens other than EDTA plasma or serum; improper labeling; samples not stored properly; samples older than stability limits; or grossly hemolyzed samples.
Methodology: High Performance Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS)
Turn Around Time: 3 to 5 days
Relative Risk – Status of Vitamin D Sufficiency:
Comment: Therapy is based on measurement of Total 25-OHD, with levels <20 ng/mL indicative of Vitamin D deficiency, while levels between 20 ng/mL and 30 ng/mL suggest insufficiency. Optimal levels are ≥30 ng/mL.
Vitamin-D is fat-soluble and therefore inadvertent or intentional ingestion of excessively high amounts could be toxic. Studies in children and adults suggest blood levels would need to exceed 150 ng/ml before there is any concern. Holick MF, Binkley NC, Bischoff-ferrari HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(7):1911-30.
Use: Monitoring vitamin D status
Clinical Significance: Vitamin D is a fat-soluble vitamin and plays a major role in calcium homeostasis. Deficiency of vitamin D and subsequent hypocalcemia have been linked to many skeletal disorders including osteoporosis. Recent studies have shown evidence that vitamin D is linked to protecting the body from a wide range of diseases. Diseases linked to vitamin D deficiency include: stroke, cardiovascular disease, osteoporosis, and several forms of cancer, multiple sclerosis, rheumatoid arthritis, and type 1 and type 2 diabetes.
Although 25-hydroxy vitamin D is further hydroxylated in the kidneys to its biologically active form, 1, 25-dihydroxy vitamin D, the half-life of 1, 25 dihydroxy vitamin D is very short and its serum levels do not correlate well with overall vitamin D levels. The measurement of serum 25-hydroxy vitamin D is the optimal indicator of biological reservoir of vitamin D.
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