The laboratory score/reference method score ratio (LSRSR) is a novel tool for monitoring laboratory performance in immunohistochemistry proficiency testing of hormone receptors in breast cancer: the CIQC experience

Getting controls under control: the time is now for immunohistochemistry

For several decades, immunohistochemistry (IHC), more specifically diagnostic IHC (dIHC), has been considered an art rather than a laboratory test. There was no clarity about what test performance characteristics are relevant to dIHC, test performance characteristics were not fully defined for dIHC and partly as a consequence of that, there were no standardised controls or reference standards. Herein, we discuss the role of standardisation of external controls for test performance characteristics and the role of standardised controls and reference standards for overall standardisation of IHC.

A reference image-based method for optimization of clinical immunohistochemistry

AIMS

Cold ischaemic and formalin fixation time (CIT and FFT) are considered to be crucial parameters for intralaboratory variation in immunohistochemistry (IHC). Here we describe a new method to optimize IHC, by using control tissue blocks with known pre-analytical history and comparing the IHC outcome with digitized reference slides.

METHODS AND RESULTS

Tissue specimens (two per tissue type) were divided into eight samples, which were subjected to different CIT and FFT. Immunohistochemistry was performed with 34 routinely used antibodies, following standard operating procedures. Relative staining intensity of four sections per slide was scored. Of the antibodies studied, seven were influenced by CIT, 13 by FFT and five by both parameters. IHC protocols were adapted until most sections on the slide showed the same intensity. Changing the antibody dilution for 10 protocols and the antigen retrieval method for six protocols improved the consistency of the IHC staining. Nine protocols could not be optimized. The optimized staining results were compared to reference slides and were found to be of adequate quality.

CONCLUSIONS

It was possible to optimize most IHC protocols by adapting the analytical, rather than the pre-analytical, phase. If global references can be established, this method could decrease interlaboratory variation, preceding standardization of the pre-analytical workflow.