Concordance and Interobserver Agreement of HercepTest™ and 4B5 Immunohistochemical Staining in Gastric Carcinoma
M L Wallander, M E Salama, S L Perkins, L J Layfield. ARUP Institute for Clinical & Experimental Pathology, Salt Lake CIty; Univeristy of Utah, Salt Lake City
Background: Reliable and reproducible detection of HER2 overexpression in gastric carcinoma is essential for determining patient eligibility for trastuzumab (Herceptin™) therapy. HercepTest™ and 4B5 immunohistochemistry (IHC) were directly compared to determine the performance characteristics of each assay for detection of HER2 status in gastric carcinoma.
Design: Twenty-six formalin-fixed, paraffin-embedded gastric adenocarcinomas were evaluated for HER2 status by IHC (HercepTest™ and 4B5) and fluorescence in situ hybridization (FISH) (PathVysion®). IHC slides were reviewed by two pathologists. Interobserver agreement and methodology concordance were determined for HercepTest and 4B5, using FISH as the gold standard.
Results: Agreement between HercepTest and 4B5 results was 81% (21/26). There was a noticeable tendency for higher scoring with 4B5 as compared to HercepTest™.
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