Overview: Fibroblast Growth Factor 23 (FGF23) TestIntroduction: The Fibroblast Growth Factor 23 (FGF23) Test measures FGF23 levels to assess bone or kidney disorders, causing bone pain or weakness. Following 2023 NKF guidelines, it uses an immunoassay for high sensitivity, aiding in metabolic screening. This test is critical for guiding diagnosis, treatment, and improving outcomes in immunology for patients with suspected bone or kidney disorders.
Other Names: FGF23 Assay, Phosphate Regulation Test.
FDA Status: Laboratory-developed test (LDT), meeting immunology standards for diagnostic accuracy.
Historical Milestone: FGF23 testing began in the 2000s with bone and kidney research. Immunoassays emerged in the 2010s, improving accuracy for metabolic disorder diagnosis.
Purpose: Diagnoses bone or kidney disorders, guides treatment, and monitors FGF23 levels in patients with bone pain or weakness.
Test Parameters: 1. Fibroblast Growth Factor 23
Pretest Condition: Fasting for 10-12 hours required to stabilize hormone levels. Collect serum or plasma in the morning. Report symptoms like bone pain or weakness, and list medications.
Specimen: 2-5 mL serum (SST) or 2-4 mL plasma (EDTA). Centrifuge within 1 hour. Transport in a biohazard bag within 8 hours.
Sample Stability at Room Temperature: 8 hours
Sample Stability at Refrigeration: 7 days
Sample Stability at Frozen: 6 months
Medical History: Document bone pain, weakness, or history of bone/kidney disorders (e.g., hypophosphatemia, CKD). Include current medications, especially phosphate binders.
Consent: Written consent required, detailing the tests purpose, diagnostic implications, and potential need for therapy.
Procedural Considerations: Uses an immunoassay to measure FGF23 levels. Results are available in 1-2 days, enabling rapid clinical decisions.
Factors Affecting Result Accuracy: Non-fasting or medications can affect results. Hemolysis may degrade samples.
Clinical Significance: Elevated FGF23 levels suggest bone or kidney disorders, prompting treatment. Normal levels may require further testing.
Specialist Consultation: Consult a nephrologist or endocrinologist for result interpretation.
Additional Supporting Tests: Phosphate levels, PTH, or bone imaging to confirm bone/kidney disorders.
Test Limitations: Results may be affected by medications or non-specific conditions. Clinical correlation is required.
References: NKF Kidney Guidelines, 2023; Kidney International, Wolf M, 2022.
