FGF 23 (Fibroblast Growth Factor 23)

Test Code

91931

CPT Codes
83520

Preferred Specimen

1 mL frozen plasma collected in an EDTA (lavender-top) tube

Patient Preparation
Fasting specimen is preferred

Minimum Volume

0.3 mL

Transport Temperature

Frozen

Specimen Stability

Room temperature: Unacceptable
Refrigerated: 6 hours
Frozen: 90 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Received room temperature

Methodology
ELISA

FDA Status
The performance characteristics of this test were determined by Pan Laboratories, Irvine, CA. It has not been cleared or approved by the U.S. Food and Drug Administration.

Setup Schedule

Set up: Mon; Report available: 1-3 days

Clinical Significance

FGF 23 is a major regulator of phosphate homeostasis. It is mainly produced in bone and also in the thymus and brain. Intact FGF 23 is biologically active. High serum FGF 23 levels stimulate FGF 23 expression. It interacts with a specific receptor in renal tubular cells, decreasing the expression of type IIa sodium/phosphate cotransponders and resulting in decreased phosphate reabsorption. FGF reduces the formation of 1, 25 dihydroxy vitamin D resulting in reduced phosphate reabsorption. When FGF 23 levels are pathologically elevated with normal renal function, hypophosphatemia with or without osteomalacia occurs. Measurement of serum FGF 23 can assist in the diagnosis and management of disorders of phosphate and bone metabolism. Human FGF 23 measurement can provide an important diagnostic tool for the laboratory evaluation of patients with a variety of hypo and hyperphosphatemic disorders.

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.