Intact Fibroblast Growth Factor 23, Serum
Use
This test is useful for diagnosing and monitoring conditions such as tumor-induced osteomalacia, X-linked hypophosphatemia, autosomal dominant hypophosphatemic rickets, and familial tumoral calcinosis with hyperphosphatemia. Measurement of fibroblast growth factor 23 (FGF23) assists in the diagnosis and management of disorders of phosphate and bone metabolism, especially in patients who have either normal or impaired kidney function. Elevated FGF23 levels are indicative of conditions such as hypophosphatemia and osteomalacia, often associated with certain benign or malignant tumors.
Special Instructions
Samples must be centrifuged and aliquoted into a plastic vial. Use the Sarstedt Aliquot Tube for collection. If not ordering electronically, complete and send one of the provided forms (Renal Diagnostics Test Request or Oncology Test Request) with the specimen.
Limitations
FGF23 concentrations must be interpreted in conjunction with serum phosphate measurements, as they can be elevated in other conditions causing hyperphosphatemia. This includes chronic kidney disease, uncontrolled type I diabetes mellitus, vitamin D toxicity, advanced malignancy, and more. It is not recommended to use FGF23 concentrations as absolute evidence of tumor-induced osteomalacia. FGF23 levels might not be elevated in all TIO cases, and alternative secretions could exist. Patients receiving certain therapies like burosumab may show prolonged elevated FGF23 levels.
New York Approved
Methodology
Immunoassay (CLIA)
Biomarkers
LOINC Codes
- 54390-0
- 54390-0
Result Turnaround Time
2-8 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
0.5 mL
Minimum Volume
0.25 mL
Container
Plastic vial
Collection Instructions
Centrifuge and aliquot serum into a plastic vial.
Causes for Rejection
Gross hemolysis, gross lipemia
Stability Requirements
| Temperature | Period |
|---|---|
| Refrigerated | 14 days |
| Frozen | 90 days |