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Test ID: 25-OH Vitamin D
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25-OH Vitamin D
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Useful For
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To diagnose vitamin D deficiency and monitor vitamin D supplementation.
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Method name and description
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Electrochemiluminescence immunoassay (ECLIA): Competetion principle
Patient specimen with reagent pretreatment 1 and 2 is incubated to release bound 25‑hydroxyvitamin D from VDBP. Pretreated sample with ruthenium‑labeled vitamin D binding protein is incubated to form a complex. A specific unlabeled antibody binds to 24,25‑dihydroxyvitamin D present in the sample and inhibits cross-reactivity to the vitamin D metabolite. After addition of streptavidin-coated microparticles and 25‑hydroxyvitamin D labeled with biotin,unbound ruthenium labeled VDBPs become occupied, a ruthenylated VDBP and the biotinylated 25‑hydroxyvitamin D complex is formed and becomes bound to the solid phase via interaction of biotin and streptavidin. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell II M. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier. Results are determined via a calibration curve which is instrument specifically generated by 2‑point calibration and a master curve.
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Clinical information
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Vitamin D is a fat-soluble steroid hormone precursor that is mainly produced in the skin by exposure to sunlight. Vitamin D is biologically inert and must undergo two successive hydroxylations in the liver and kidney to become the biologically active 1, 25‑dihydroxyvitamin D. Most of the 25‑hydroxyvitamin D, measurable in serum, is 25‑hydroxyvitamin D3 whereas 25‑hydroxyvitamin D2 reaches measurable levels only in patients taking vitamin D2 supplements.
Vitamin D is responsible for bone health. In children, severe deficiency leads to bone-malformation, known as rickets. Milder degrees of insufficiency are believed to cause reduced efficiency in the utilization of dietary calcium. Vitamin D deficiency causes muscle weakness; in elderly, the risk of falling has been attributed to the effect of vitamin D on muscle function.
Vitamin D deficiency is a common cause of secondary hyperparathyroidism. Elevations of parathyroid hormone levels, especially in elderly vitamin D deficient adults can result in osteomalacia, increased bone turnover, reduced bone mass and risk of bone fractures.
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Specimen type / Specimen volume / Specimen container
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Specimen type: Serum, Plasma
Minimum volume of sample: 1 mL
Serum: Plain tube (red or yellow top)
Plasma: Li‑heparin tube
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Collection instructions / Special Precautions / Timing of collection
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Collect blood by standard venipuncture techniques as per specimen requirements. When processing samples in primary tubes (sample collection systems), follow the instructions of the tube manufacturer.
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Storage and transport instructions
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Storage: 4 days at 2 – 8°C
8 hours at 20 – 25°C
24 weeks at ‑20 °C (± 5 °C)
Transport: 2-25°C
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Specimen Rejection Criteria
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Grossly hemolyzed, icteric and lipemic samples, wrong collection container, insufficient sample and heat‑inactivated samples.
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Biological reference intervals and clinical decision values
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Interpretative Data:
Please note the change from population-based reference range to clinical decision values. Clinical decision values correlate better with clinical status of Vitamin D.
Deficiency: < 12 ng/mL
Insufficiency: 12 - 19 ng/mL
Optimum Values: ≥ 20 ng/ml
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Turnaround time / Days and times test performed / Specimen retention time
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Daily (24/7)
Turn-around time:
Routine: One working day
Specimen Retention: 4 days
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