Download Søren Nielsen Scheme Manager NordiQC Immunohistochemistry

Søren Nielsen
Scheme Manager
NordiQC
Immunohistochemistry (IHC) is a routinely applied assay in surgical and clinical pathology, and
essential in the diagnosis and sub-classification of many neoplasias. Despite being extensively
used for more than 40 years, lack of standardization is a huge problem. Multiple parameters in the
pre-analytical, analytical and post-analytical phase and the choices made for each of these by the
laboratory will affect the final result. In order to evaluate the level of inter-laboratory consistency of
IHC mainly focusing on the analytical part, Nordic immunohistochemical Quality Control (NordiQC)
was established in 2003. In total more than 26.000 IHC slides have been evaluated in the elevenyear period 2003-2013. In each assessment run 15 to more than 300 laboratories have
participated. Over-all, seventy-one percent of the staining results assessed have been evaluated
as sufficient for diagnostic use, while twenty-nine percent as insufficient. All IHC protocols used for
the stained slides submitted to NordiQC have been analyzed focusing on the technical calibration
performed by the laboratories, and specific parameters giving sufficient and insufficient results
have been identified. The most common causes giving insufficient results were: Inadequate
calibration of the primary antibody, usage of a less successful primary antibody, inappropriate
choice of epitope retrieval method, insufficient heat induced epitope retrieval and inadequate
detection kit. About ninety percent of the insufficient results were characterized by a generally too
weak signal or false negative staining reaction, whereas in the remaining ten percent a poor signalto-noise ratio or false positive staining results were seen. Identification of recommendable positive
and negative tissue controls to ensure an appropriate calibration of the IHC assay in combination
with individually tailored suggestions for protocol optimization have for many markers improved the
IHC staining results and thus the inter-laboratory consistency of the IHC results for these. The
overall data generated by NordiQC through eleven years clearly indicates that external quality
assessment is a valuable and necessary supplement to internal quality control.