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Test Code FGF23 Level Fibroblast Growth Factor 23 (FGF23), Plasma

Reporting Name

Fibroblast Growth Factor 23, P

Useful For

Diagnosing and monitoring oncogenic osteomalacia


Possible localization of occult neoplasms causing oncogenic osteomalacia


Diagnosing X-linked hypophosphatemia or autosomal dominant hypophosphatemic rickets


Diagnosing familial tumoral calcinosis with hyperphosphatemia


Predicting treatment response to calcitriol or vitamin D analogs in patients with renal failure

Specimen Required

Collection Container/Tube: Lavender top (EDTA)

Submission Container/Tube: Plastic vial

Specimen Volume: 1.5 mL

Specimen Type

Plasma EDTA

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma EDTA Frozen (preferred) 90 days
  Refrigerated  14 days

Day(s) and Time(s) Performed

Tuesday,Thursday; 10 a.m.

Seattle Children's Hospital Note:

TAT: 3 - 10 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

Method Name

Immunometric Enzyme Assay

Method Description

The kit uses 2 affinity-purified goat antibodies that bind at the carboxy terminal portion of fibroblast growth factor 23 (FGF23). One antibody is coated onto microtiter wells and the other is biotinylated. Horseradish peroxide conjugated to avidin and 3.3', 5,5'-tetramethylbenzidine (TMB) substrate provide the colored product, which is read in a microtiter plate spectrophotometer.(Jonsson KB. Zahradnik R. Larsson T, et al: Fibroblast growth factor 23 in oncogenic osteomalacia and X-linked hypophosphatemia. N Engl J Med 2003;348:1656-1663)

Reference Values

Results may be significantly elevated (ie, >900 RU/mL) in normal infants <3 months of age.

3 months-17 years: ≤230 RU/mL

≥18 years: ≤180 RU/mL

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
FGF23 Fibroblast Growth Factor 23, P 46699-5


Result ID Test Result Name Result LOINC Value
88662 Fibroblast Growth Factor 23, P 46699-5

Reject Due To


Mild OK; Gross reject


Mild OK; Gross OK


Mild OK; Gross OK