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External quality assessment for immunohistochemistry: experiences from NordiQC
1Institute of Pathology, Aalborg University Hospital , Aalborg , Denmark.
Insights
External quality assessment for immunohistochemistry (IHC) revealed that 29% of staining results were insufficient for diagnosis. Key issues included antibody calibration and epitope retrieval, highlighting the need for standardization in IHC protocols.
Area of Science:
- Pathology
- Laboratory Medicine
- Biotechnology
Background:
- Immunohistochemistry (IHC) is crucial for diagnosing neoplastic lesions but suffers from a lack of standardization.
- Pre-analytical, analytical, and post-analytical factors significantly impact IHC staining results.
- Nordic immunohistochemical Quality Control (NordiQC) was established to address inter-laboratory consistency in IHC.
Purpose of the Study:
- To evaluate the inter-laboratory consistency of immunohistochemistry (IHC) staining.
- To identify common causes of insufficient IHC staining results.
- To assess the impact of external quality assessment on IHC standardization.
Main Methods:
- NordiQC evaluated over 26,000 IHC slides from 2003-2013.
- Participating laboratories (15-300 per assessment) submitted IHC slides and protocols.
- Staining results and protocols were assessed for diagnostic adequacy and technical calibration.
Main Results:
- 71% of IHC staining results were sufficient for diagnostic use; 29% were insufficient.
- Common causes for insufficient results included primary antibody issues and inadequate epitope retrieval.
- Weak signals or false negatives (90%) were more prevalent than poor signal-to-noise or false positives (10%).
Conclusions:
- External quality assessment, like NordiQC, is vital for improving IHC standardization and inter-laboratory consistency.
- Optimized protocols and the use of tissue controls enhance IHC assay calibration and diagnostic accuracy.
- Standardization efforts are essential to overcome the challenges in IHC pre-analytical, analytical, and post-analytical phases.
Abstract:
Immunohistochemistry (IHC) is applied routinely in surgical and clinical pathology, because it is essential for diagnosis and sub-classification of many neoplastic lesions. Despite its extensive use for more than 40 years, lack of standardization is a major problem; many factors during the pre-analytical, analytical and post-analytical phases affect the final results. Nordic immunohistochemical Quality Control (NordiQC) was established in 2003 to evaluate the inter-laboratory consistency of IHC, focusing mainly on the analytical part. More than 26,000 IHC slides have been evaluated during the period 2003-2013; 15 - 300 laboratories have participated in each assessment. Overall, 71% of the staining results assessed have been evaluated as sufficient for diagnostic use, while 29% were judged insufficient. All IHC protocols used for the stained slides submitted to NordiQC have been evaluated by focusing on the technical calibration performed by the laboratories, and specific parameters that gave sufficient or insufficient results have been identified. The most common causes for insufficient results were: inadequate calibration of the primary antibody, use of an inadequate primary antibody, inappropriate choice of epitope retrieval method, insufficient heat induced epitope retrieval (HIER) and use of an inadequate detection kit. Approximately 90% of the insufficient results were characterized by either a signal that was too weak or false negative staining, whereas in the remaining 10%, a poor signal-to-noise ratio or false positive staining was seen. Identification of positive and negative tissue controls to ensure appropriate calibration of the IHC assay combined with individually tailored suggestions for protocol optimization have improved IHC staining for many markers and thus inter-laboratory consistency of the IHC results. The overall data generated by NordiQC during 11 years clearly indicates that external quality assessment is a valuable and necessary supplement to internal quality control.
