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Test ID GFAP Glial Fibrillary Acidic Protein Immunostain, Technical Component Only

Ordering Guidance

This test includes only technical performance of the stain (no pathologist interpretation is performed). If diagnostic consultation by a pathologist is required order PATHC / Pathology Consultation.

Shipping Instructions

Attach the green pathology address label and the pink Immunostain Technical Only label included in the kit to the outside of the transport container.

Specimen Required

Supplies: Immunostain Technical Only Envelope (T693)

Specimen Type: Tissue

Container/Tube: Immunostain Technical Only Envelope

Preferred: 2 Unstained positively charged glass slide (25- x 75- x 1-mm) per test ordered; sections 4-microns thick

Acceptable: Formalin-fixed, paraffin-embedded (FFPE) tissue block

Useful For

Classification of glial tumors

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
IHTOI IHC Initial, Tech Only No No
IHTOA IHC Additional, Tech Only No No

Method Name

Immunohistochemistry (IHC)

Reporting Name

GFAP IHC, Tech Only

Specimen Type


Specimen Stability Information

Specimen Type Temperature Time Special Container
TECHONLY Ambient (preferred)

Clinical Information

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein of 52 kDa found in glial cells, astrocytes, and ependymal cells. Immunoperoxidase staining for GFAP produces intense cytoplasmic staining of astrocytes, glial cells, and ependymal cells in normal brain. In neoplastic tissues, GFAP is useful for the identification of glial tumors such as astrocytomas and ependymomas.


This test does not include pathologist interpretation, only technical performance of the stain. If interpretation is required order PATHC / Pathology Consultation for a full diagnostic evaluation or second opinion of the case.


The positive and negative controls are verified as showing appropriate immunoreactivity and documentation is retained at Mayo Clinic Rochester. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request; call 855-516-8404.


Interpretation of this test should be performed in the context of the patient's clinical history and other diagnostic tests by a qualified pathologist.

Clinical Reference

1. Goyal R, Mathur SK, Gupta S, et al: Immunohistochemical expression of glial fibrillary acidic protein and CAM5. 2 in glial tumors and their role in differentiating glial tumors from metastatic tumors of central nervous system. J Neurosci Rural Pract. Oct-Dec 2015;6(4):499-503

2. Zhao J, Wang B, Huang T, et al: Glial response in early stages of traumatic brain injury. Neurosci Lett. 2019 Aug 24;708:134335

3. Magaki SD, Williams CK, Vinters HV: Glial function (and dysfunction) in the normal and ischemic brain. Neuropharmacology. 2018 May 15;134(Pt B):218-225

Day(s) Performed

Monday through Friday

Report Available

1 to 3 days

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

88342-TC, primary

88341-TC, if additional IHC

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GFAP GFAP IHC, Tech Only Order only;no result


Result ID Test Result Name Result LOINC Value
70756 GFAP IHC, Tech Only Bill only; no result


If not ordering electronically, complete, print, and send a Immunohistochemical (IHC)/In Situ Hybridization (ISH) Stains Request (T763) with the specimen.

Testing Algorithm

For the initial technical component only immunohistochemical (IHC) stain performed, the appropriate bill-only test ID will be reflexed and charged (IHTOI). For each additional technical component only IHC stain performed, an additional bill-only test ID will be reflexed and charged (IHTOA).

Mayo Clinic Laboratories | IHC Catalog Additional Information: