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Test Code EXT2 Exostosin 2 (EXT2) 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 "Attention Pathology" address label (T498) and the pink Immunostain Technical Only label included in the kit to the outside of the transport container.



Specimen Required


Specimen Type: Tissue

Supplies: Immunostain Technical Only Envelope (T693)

Container/Tube: Immunostain Technical Only Envelope

Preferred:

-Formalin-fixed, paraffin-embedded tissue block

OR

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

Acceptable: None


Secondary ID

614548

Useful For

Identification of exostosin 2 associated membranous nephropathy

Reflex Tests

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

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).

Method Name

Immunohistochemistry (IHC)

Reporting Name

EXT2 IHC, Tech Only

Specimen Type

TECHONLY

Specimen Stability Information

Specimen Type Temperature Time Special Container
TECHONLY Ambient (preferred)
  Refrigerated 

Reject Due To

Wet/frozen tissue
Cytology smears
Nonformalin fixed tissue
Nonparaffin embedded tissue
Noncharged slides
ProbeOn slides
Snowcoat slides		 Reject

Clinical Information

Primary membranous nephropathy is an autoimmune disease of the kidney where antibodies target an antigen in the glomerular basement membrane resulting in kidney damage or failure. In up to 75% of primary membranous nephropathy cases phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A) are the target antigens. Exostosin 1 (EXT1) and exostosin 2 (EXT2), a recently identified set of novel proteins are associated with a subset of PLA2R and TSD7A double-negative MN. EXT1 and EXT2 may represent the target antigens or biomarker proteins of secondary (autoimmune) MN.

Interpretation

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. 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.

Cautions

Age of a cut paraffin section can affect immunoreactivity. Stability thresholds vary widely among published literature and are antigen dependent. Best practice is for paraffin sections to be cut within 6 weeks.

 

The charge of glass slides can be affected by environmental factors and subsequently may alter slide staining. Sending unsuitable glass slides can result in inconsistent staining due to poor slide surface chemistry.

 

Best practices for storage of positively charged slides:

-Minimize time slides are stored after being unpackaged

-Limit exposure to high humidity and heat

-Minimize exposure to plastics

Clinical Reference

1. Bobart SA, Tehranian S, Sethi S, et al. A target antigen-based approach to the classification of membranous nephropathy. Mayo Clin Proc. 2021;96(3):577-591

2. Ravindran A, Moura MC, Fervenza FC, et al. In Patients with membranous lupus nephritis, exostosin-positivity and exostosin-negativity represent two different phenotypes. JASN. 2021;32(3):695-706

3. Sethi S, Madden BJ, Debiec H, et al. Exostosin1/exostosin 2-associated membranous nephropathy. JASN. 2019;30(6):1123-1136

4. Magaki S, Hojat SA, Wei B, So A, Yong WH. An Introduction to the Performance of Immunohistochemistry. Methods Mol Biol. 2019;1897:289-298. doi:10.1007/978-1-4939-8935-5_25

Method Description

Immunohistochemistry on sections of paraffin-embedded tissue.(Unpublished Mayo method)

Day(s) Performed

Monday through Friday

Report Available

1 to 3 days

Specimen Retention Time

Until staining is complete.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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

Result ID Test Result Name Result LOINC Value
614549 EXT2 IHC, Tech Only No LOINC Needed

Forms

If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) or Immunohistochemical (IHC)/In Situ Hybridization (ISH) Stains Request (T763) with the specimen.