Section 2 -

United Kingdom External Quality Assurance (UKNEQAS) Schemes for HER2 IHC and FISH Testing: the Value of Regular Participation and Educational Feedback Bharat Jasani Department of Pathology, School of Medicine Cardiff University Cardiff, Wales Merdol Ibrahim & Keith Miller UKNEQAS for IHC Advanced Diagnostics Laboratory University College London London, England, U.K.

Click here to download handout in pdf format for the current section (286 KB) Background: HER2 Immunohistochemistry (HER2 IHC) in combination with HER2 fluorescence in situ hybridization (HER2 FISH) is considered to be a pre-requisite for selection for Herceptin (Trastuzumab) based treatment of both early and advanced breast cancer. The high cost of the drug and a 4-fold increased risk of cardiotoxic side effect in anthracycline treated patients, has emphasised the need for using reliable and accurate assay methods. Design: The reliability of an assay is dependent on a variety of technical factors associated with the pre-examination, examination and post-examination phases of analysis. Accuracy of testing is in addition dependent on the interpretation and reporting skills of the operator as well as the clinical validity of the assay used. In the pre-examination phase the quality of formaldehyde fixation and section thickness appear to be amongst the most important factors influencing the reliability of the assay. The critical factors in the examination phase have been identified to be the strength of antigen retrieval, the quality and the titration of the primary antibody and the power of the secondary detection method employed. The post-examination phase is predominantly affected by quality of the haematoxylin counter-staining and the nature of the biopsy material (e.g. core vs excision) made available for diagnosis. In order to assess the relative contribution of these factors to assay performance, the UKNEQAS, in association with Novocastra, Newcastle, England, has developed buffered formaldehyde fixed paraffin embedded cell line blocks containing 4 cell lines, (SK-BR-3, MDA-MB-453, MDA-MB-175, & MDA-MB-231) which express HER2 IHC membrane staining levels of 3+, 2+, 1+ & 0, respectively. Two slides bearing the cell line block sections are distributed per run to each participant laboratory four times a year. The technically better stained of the two slides is requested to be returned, together with their own in-house control(s), to the UKNEQAS ICC for assessment. Slides are evaluated anonymously by a panel of 4 expert assessors (Pathologists and Biomedical Scientists). The overall result and the scores of each assessor together with possible explanations for any poor quality performance are returned confidentially to the participant . Results are collated and distributed to all participants in the UKNEQAS Scheme Journal which shows the variety of methods used by all participating laboratories. Two randomly selected best methods from participants' own results are also highlighted in the Journal. Results: From the 10 runs completed so far over a period of the past three years, the quality of antigen retrieval method and haematoxylin counterstaining have often proved to be the major factors influencing the technical quality of HER2 IHC staining. Conclusion: UKNEQAS has established an effective process for feeding back HER2 IHC performance results to participant laboratories in a timely fashion. Recently it has initiated an EQA scheme for HER2 FISH testing/interpretation and is also planning to introduce a separate scheme for assuring quality of the interpretation of HER2 IHC.