Improved breast cancer biomarker detection through a simple, high frequency, low cost external proficiency testing program

Aims: We describe a simple, low cost, high frequency immunohistochemistry external proficiency testing program, and show how its use can lead to improved breast cancer biomarker detection. Methods: Over a 30 month period in British Columbia, Canada, we used tissue microarray slides to follow the performance of twelve clinical laboratories in nine separate external proficiency testing runs. Sensitivity for detection of oestrogen receptor (ER), progesterone receptor (PR), and HER2 were calculated for each laboratory, biomarker, and run. Results: Mean sensitivities for detection of ER, PR, and HER2 were 97.1%, 84.8%, and 90.7%, respectively. HER2 sensitivity improved over time, from 87.0% to 92.9% (p=0.04), with a trend towards improvement seen for PR (81.9-88.1%, p=0.13). ER sensitivities were high throughout the test period. Improvements occurred without mandating any specific laboratory changes. Conclusions: This simple, low cost, high frequency external proficiency testing program is highly sustainable and can be implemented in any multi-institutional group or region.