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Genetic Labs

Houston, Texas

Genetic Laboratory
Medical Genetics Laboratories
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Medical Genetics Test Details

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Vitamin D (25-hydroxyvitamin D2 and D3)
Test Information: Summary: This test provides quantitative analysis of plasma 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 levels for diagnosis of vitamin D deficiency, differential diagnosis of causes of rickets, and management of vitamin D therapy/patient compliance.

Vitamin D is a family of fat-soluble compounds derived either from cholesterol or ergosterol. Vitamin D is obtained from diet, and we can make it when exposed to ultraviolet radiation found in sunlight. The vitamin D that we make ourselves and that which we get from animal food sources is vitamin D3, or cholecalciferol, which is made from cholesterol. The vitamin D that we obtain from invertebrates and plants is vitamin D2, which is made from ergosterol. Once absorbed into the body, the vitamin D is rapidly hydroxylated by the liver, producing hydroxy vitamin D, which is then transported in the blood. The measurement of this plasma or serum 25-hydroxy vitamin D represents a good measure of the total vitamin D status of an individual.

Accumulating evidence demonstrates that vitamin D deficiency is highly prevalent worldwide. In its clinical practice guideline published in 2011, The Endocrine Society recommends using the serum 25-hydroxyvitamin D level to evaluate vitamin D status in patients who are at risk for vitamin D deficiency. Measurement of 25(OH)-vitamin D2 monitors the supplementation and exogenous intake of vitamin D; whereas 25(OH)-vitamin D3 is a measure of endogenous vitamin D.

Vitamin D levels have routinely been determined using immunoassays for many years and often provide inconsistent results. These assays suffer from cross-reactivity of the antibodies used and the inability to differentiate 25(OH)-D2 from 25(OH)-D3. Measurement of 25(OH)-vitamin D2 monitors the supplementation and exogenous intake of of vitamin D; whereas 25(OH)-vitamin D3 is a measure of endogenous vitamin D. This procedure uses Ultra Performance Liquid Chromatography (UPLC) coupled with multiple reaction monitoring (MRM) tandem mass spectrometry to differentiate and quantify the analytes. Our assay measures 25-hydroxyvitamin D2 and D3 by UPLC-MS/MS with an isotopic internal standard. Reference material (SRM 972 Vitamin D in Human Serum) from National Institute of Standard and Technology (NIST) is used for the assay calibration. This procedure is the gold standard for diagnosing vitamin D deficiency and monitoring vitamin D supplementation.
Test Details
Test Code: 4360
Special Notes: Only samples from patients age 1 year and above are accepted at this time for the testing.
Technical Information
Methodology: UPLC-Tandem Mass Spectroscopy
Test Type: Analyte Analysis
References Values or Ranges: Ranges are provided in the report.
Sample & Shipping Information
Test Requisition: Biochemical
Specimen Type: Plasma
Requirements: Draw blood in a Heparin (green-top) tube(s) and separate as soon as possible. Send 1-2 cc of plasma. Store the specimen frozen at -20C. Specimen may be stored frozen for up to 7 days.
Shipping Conditions: Ship frozen on 3-5 lbs of dry ice in an insulated container by overnight courier.

Specimen Type: Serum
Requirements: Draw blood in a No Additive (red-top) or Serum Gel (red/gray-top) tube(s) and separate as soon as possible. Send 1-2 cc of serum. Store the specimen frozen at -20C.
Shipping Conditions: Ship frozen on dry ice in an insulated container by overnight courier.

Turn Around Time: 8 days
Billing Information
List Price: *For Insurance or Institutional Prices, please call.
CPT Codes: 82306 x 1


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