Overview: Vitamin D 25-Hydroxy TestIntroduction: The Vitamin D 25-Hydroxy Test measures 25-hydroxy vitamin D to diagnose deficiency, causing bone pain. Following 2023 Endocrine Society guidelines, it uses biochemical methods for high specificity, supporting metabolic screening. This test is critical for guiding diagnosis, treatment planning, and improving outcomes in biochemistry for patients with suspected vitamin D deficiency.
Other Names: 25-Hydroxy Vitamin D Assay, 25-OH Vitamin D Test.
FDA Status: Laboratory-developed test (LDT), meeting biochemistry standards for diagnostic accuracy.
Historical Milestone: 25-Hydroxy vitamin D testing began in the 1970s with bone metabolism research. Biochemical methods improved in the 2000s, enhancing diagnostic precision.
Purpose: Measures 25-hydroxy vitamin D to diagnose deficiency, guides treatment, and evaluates patients with bone pain.
Test Parameters: 1. 25-Hydroxy Vitamin D Level
Pretest Condition: Fasting for 10-12 hours required. Collect serum or plasma. Report history of bone pain or vitamin D deficiency.
Specimen: Serum (SST, 2-5 mL), Plasma (EDTA, 2-4 mL). Transport in a biohazard container.
Sample Stability at Room Temperature: 8 hours
Sample Stability at Refrigeration: 7 days
Sample Stability at Frozen: 6 months
Medical History: Document bone pain, fatigue, or history of vitamin D deficiency. Include current medications, especially vitamin D supplements.
Consent: Written consent required, detailing the tests purpose, vitamin D deficiency implications, and risks of sample collection.
Procedural Considerations: Uses chemiluminescence or LC-MS to measure 25-hydroxy vitamin D levels. Results are available in 1-2 days, supporting clinical decisions. Performed in laboratories, often for vitamin D deficiency diagnosis.
Factors Affecting Result Accuracy: Improper fasting or sample hemolysis can affect results. Sun exposure or supplements may alter levels.
Clinical Significance: Low 25-hydroxy vitamin D confirms deficiency, guiding supplementation therapy. Normal levels may require 1,25-dihydroxy vitamin D testing.
Specialist Consultation: Consult an endocrinologist for result interpretation and treatment planning.
Additional Supporting Tests: 1,25-Dihydroxy vitamin D, calcium levels, or bone density scan to confirm vitamin D deficiency diagnosis.
Test Limitations: Non-specific for deficiency cause; clinical correlation is needed. Sample quality affects sensitivity.
References: Endocrine Society Vitamin D Guidelines, 2023; Journal of Clinical Endocrinology, Bikle DD, 2022.
