Review ArticleEvolution of Quality Assurance for Clinical Immunohistochemistry in the Era of Precision Medicine: Part 1: Fit-for-Purpose Approach to Classification of Clinical Immunohistochemistry BiomarkersCheung, Carol C. MD, PhD, JD*†; D’Arrigo, Corrado MB, ChB, PhD, FRCPath‡§∥; Dietel, Manfred MD, PhD¶; Francis, Glenn D. MBBS, FRCPA, MBA, FFSc (RCPA)#,**,††; Gilks, C. Blake MD‡‡; Hall, Jacqueline A. PhD§§,∥∥; Hornick, Jason L. MD, PhD¶¶; Ibrahim, Merdol PhD##; Marchetti, Antonio MD, PhD***; Miller, Keith FIBMS##; van Krieken, J. Han MD, PhD†††; Nielsen, Soren BMS‡‡‡,§§§; Swanson, Paul E. MD∥∥∥; Taylor, Clive R. MD¶¶¶; Vyberg, Mogens MD‡‡‡,§§§; Zhou, Xiaoge MD###,****; Torlakovic, Emina E. MD, PhD*,††††,‡‡‡‡; From the International Society for Immunohistochemistry and Molecular Morphology (ISIMM) and International Quality Network for Pathology (IQN Path)Author Information *Department of Laboratory Medicine and Pathobiology, University of Toronto †Department of Pathology, University Health Network ††††Department of Laboratory Hematology, University Health Network, Toronto, ON ‡‡Vancouver General Hospital, University of British Columbia, Vancouver, BC ∥∥∥Department of Pathology and Laboratory Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada ‡Poundbury Cancer Institute §Dorset County Hospital NHS Foundation Trust ∥Cancer Diagnostic Quality Assurance Services (CADQAScic), Dorchester ∥∥Division of Cancer, Department of Surgery & Cancer, Imperial College, London, UK ##UK National External Quality Assessment Scheme (UK NEQAS), University College London, London, UK ¶School of Medicine, Institute of Pathology, Charité—University Hospital Berlin, Berlin, Germany #Griffith University, Gold Coast **RCPA Quality Assurance Program, Sydney ††Genomics For Life, Brisbane, Australia §§International Quality Network for Pathology (IQN Path), Luxembourg City, Luxembourg ¶¶Brigham and Women’s Hospital, Harvard Medical School, Boston, MA ***Center of Predictive Molecular Medicine, Center for Excellence on Ageing and Translational Medicine, University of Chieti-Pescara, Chieti, Italy †††Department of Pathology, Radboud University Medical Centre, Nijmegen, The Netherlands ‡‡‡Institute of Pathology, Aalborg University Hospital and Department of Clinical Medicine, Aalborg University §§§Nordic Immunohistochemistry Quality Control (NordiQC), Aalborg, Denmark ¶¶¶Keck School of Medicine, University of Southern California, Los Angeles, CA ###Department of Pathology, Beijing Friendship Hospital, Capital Medical University, Beijing, China ****Chinese Committee for Pathologists—Immunohistochemistry Quality Control ‡‡‡‡Canadian Immunohistochemistry Quality Control (CIQC)/Canadian Association of Pathologists National Standards Committee for High Complexity Testing/Immunohistochemistry, Vancouver, BC, Canada The authors declare no conflict of interest. Reprints: Emina E. Torlakovic, MD, PhD, Department of Laboratory Hematology, Toronto General Hospital/UHN, 200 Elizabeth Street, Toronto, ON, Canada M5G 2C4 (e-mail: email@example.com). Applied Immunohistochemistry & Molecular Morphology: January 2017 - Volume 25 - Issue 1 - p 4-11 doi: 10.1097/PAI.0000000000000451 Buy Metrics Abstract Technical progress in immunohistochemistry (IHC) as well as the increased utility of IHC for biomarker testing in precision medicine avails us of the opportunity to reassess clinical IHC as a laboratory test and its proper characterization as a special type of immunoassay. IHC, as used in current clinical applications, is a descriptive, qualitative, cell-based, usually nonlinear, in situ protein immunoassay, for which the readout of the results is principally performed by pathologists rather than by the instruments on which the immunoassay is performed. This modus operandi is in contrast to other assays where the instrument also performs the readout of the test result (eg, nephelometry readers, mass spectrometry readers, etc.). The readouts (results) of IHC tests are used either by pathologists for diagnostic purposes or by treating physicians (eg, oncologists) for patient management decisions, the need for further testing, or follow-up. This paper highlights the distinction between the original purpose for which an IHC test is developed and its subsequent clinical uses, as well as the role of pathologists in the analytical and postanalytical phases of IHC testing. This paper is the first of a 4-part series, under the general title of “Evolution of Quality Assurance for Clinical Immunohistochemistry in the Era of Precision Medicine.” Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.