Original ArticlesQuantification of Human Epidermal Growth Factor Receptor 2 Immunohistochemistry Using the Ventana Image Analysis System Correlation With Gene Amplification by Fluorescence In Situ Hybridization The Importance of Instrument Validation for Achieving High (>95%) Concordance RateDennis, Jake MD; Parsa, Rezvaneh CT (ASCP); Chau, Donnie CT (ASCP); Koduru, Prasad PhD; Peng, Yan MD, PhD; Fang, Yisheng MD, PhD; Sarode, Venetia Rumnong MDAuthor Information Department of Pathology, UT Southwestern Medical Center, Dallas, TX A portion of this paper was presented in poster format at the United States and Canadian Association of Pathologists (USCAP) meeting in Baltimore, MD, March 7, 2013 by J.D. He received the USCAP pathologist-in-training award ($500) from the Association of Directors of Anatomic and Surgical Pathology. Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Venetia Rumnong Sarode, MD, Department of Pathology, UT Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd. Dallas, TX 75390 (e-mail: [email protected]). The American Journal of Surgical Pathology: May 2015 - Volume 39 - Issue 5 - p 624-631 doi: 10.1097/PAS.0000000000000375 Buy Metrics Abstract The use of computer-based image analysis for scoring human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) has gained a lot of interest recently. We investigated the performance of the Ventana Image Analysis System (VIAS) in HER2 quantification by IHC and its correlation with fluorescence in situ hybridization (FISH). We specifically compared the 3+ IHC results using the manufacturer’s machine score cutoffs versus laboratory-defined cutoffs with the FISH assay. Using the manufacturer’s 3+ cutoff (VIAS score; 2.51 to 3.5), 181/536 (33.7%) were scored 3+, and FISH was positive in 147/181 (81.2%), 2 (1.1%) were equivocal, and 32 (17.6%) were FISH (−). Using the laboratory-defined 3+ cutoff (VIAS score 3.5), 52 (28.7%) cases were downgraded to 2+, of which 29 (55.7%) were FISH (−), and 23 (44.2%) were FISH (+). With the revised cutoff, there were improvements in the concordance rate from 89.1% to 97.0% and in the positive predictive value from 82.1% to 97.6%. The false-positive rate for 3+ decreased from 9.0% to 0.8%. Six of 175 (3.4%) IHC (−) cases were FISH (+). Three cases with a VIAS score 3.5 showed polysomy of chromosome 17. In conclusion, the VIAS may be a valuable tool for assisting pathologists in HER2 scoring; however, the positive cutoff defined by the manufacturer is associated with a high false-positive rate. This study highlights the importance of instrument validation/calibration to reduce false-positive results. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.