Proficiency testing in immunohistochemistry—experiences from Nordic Immunohistochemical Quality Control (NordiQC)

Mogens Vyberg,Søren Nielsen

doi:10.1007/s00428-015-1829-1

Abstract

Despite extensive use of immunohistochemistry (IHC) for decades, lack of standardization remains a major problem, even aggravated in the era of targeted therapy. Nordic Immunohistochemical Quality Control (NordiQC) is an international academic proficiency testing (PT) program established in 2003 primarily aimed at assessing the analytical phases of the laboratory IHC quality. About 700 laboratories from 80 countries are currently participating. More than 30,000 IHC slides have been evaluated during 2003–2015. Overall, about 20 % of the staining results in the breast cancer IHC module and about 30 % in the general module have been assessed as insufficient for diagnostic use. The most common causes for insufficient results are less successful antibodies (poor and less robust antibodies, poorly calibrated ready-to-use (RTU) products, and stainer platform-dependent antibodies; 17 %), insufficiently calibrated antibody dilutions (20 %), insufficient or erroneous epitope retrieval (27 %), less sensitive visualization systems (19 %), and other (heat- and proteolysis-induced impaired morphology, endogenous biotin reaction, drying out phenomena, stainer platform-dependant protocol issues; 17 %). Approximately, 90 % of the insufficient results are characterized by either a too weak or false negative staining, whereas in the remaining 10 %, a poor signal-to-noise ratio or false positive staining is seen. Individually tailored recommendations for protocol optimization and identification of best tissue controls to ensure appropriate calibration of the IHC assay have for many markers improved IHC staining as well as inter-laboratory consistency of the IHC results. RTUs will not always provide an optimal result and data sheets frequently misguide the laboratories hampering the improvement in IHC quality. The overall data generated by NordiQC during 12 years indicates that continuous PT is valuable and necessary. Detailed description of the results of the NordiQC programme is available on www.nordiqc.org and summarized in this paper.

Highlights

Immunohistochemistry is technically complex, and no aspect of this complexity can be ignored, from the moment of collecting the specimen to issuance of the final report [1].During the last four decades in pathology, immunohistochemistry (IHC) has developed into an indispensable ancillary diagnostic tool, in the classification of neoplastic lesions
The Nordic Immunohistochemical Quality Control (NordiQC) external quality assurance (EQA) scheme consists of three modules: (1) general module that includes tests for the most common epitopes demonstrated in surgical and clinical pathology to identify and subclassify neoplasms being performed in three runs per year, each comprising 5–6 tests; (2) breast cancer IHC module that includes tests for HER2, hormone receptors, and other markers relevant in breast cancer pathology being performed in two runs per year; and (3) breast cancer HER2 in situ hybridization (ISH) module, in two runs per year
CyclinD1 (CyD1) Cytokeratin (CK) 5 CK 7 CK 19 CK 20 CK, high molecular weight CK, low molecular weight CK, panDesmin Detected on GIST-1 (DOG1, anoctamin-1) E-cadherin Epithelial cell adhesion molecule (EpCAM) Epithelial membrane antigen (EMA) Estrogen receptor alpha (ER) Factor VIII related antigen GATA3 Glial fibrillary acidic protein (GFAP) Glypican 3 Gross cystic disease fluid protein-15 (GCDFP15) HER-2

Summary

Introduction

During the last four decades in pathology, immunohistochemistry (IHC) has developed into an indispensable ancillary diagnostic tool (class I assay), in the classification of neoplastic lesions. While the potential of IHC in pathology is universally accepted, it is still considered a “special stain” developed in the individual laboratory rather than a tissue-based qualitative or quantitative immunoassay, and its reliability is compromised by lack of standardization, causing a high risk of suboptimal laboratory performance which leads to inferior pathology diagnostics. Internal quality control is focused on the consistency of the IHC assays, but does generally not give information about the technical or diagnostic quality, and insufficient assays often pass unnoticed through the laboratory validation because of improper control tissues or lack of knowledge about reaction patterns

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