A new immunohistochemical ER/PR image analysis system: a multisite performance study

Aperio provides a new image analysis (IA) solution for immunohistochemistry (IHC) as part of its digital pathology system. To be used in a clinical setting, substantial equivalence to scoring by manual microscopy (MM) needs to be shown. A multisite study was conducted to assess the performance of Aperio's IHC IA solution for estrogen receptor (ER) and progesterone receptor (PR).

A total of 260 formalin-fixed, paraffin-embedded breast tissue specimens were assayed at 2 clinical sites for ER and PR. The ability to score ER/PR slides in terms of (1) percentage of positive nuclei with cutoffs of 1%, 5%, and 10% and (2) average staining intensity as 0, 1+, 2+, and 3+ score was assessed. At each site, 3 pathologists performed a blinded read of the glass slides using their microscopes. The glass slides were then scanned, and after a wash-out period and randomization of the slides, the pathologists viewed the images on a computer monitor and outlined a representative set of tumor regions to be analyzed by IA. Each of the methods: MM and IA were evaluated separately and comparatively.

Comparable or higher percent agreements were obtained for IA compared with MM (ER--percent of positive nuclei with cutoffs: MM: 91.3% to 98.8%/IA: 93.8% to 98.8%/IA vs. MM: 92.5% to 97.5%, and intensity score: MM: 55.0% to 86.3%/IA: 88.8% to 90.0%/IA vs. MM: 63.8% to 86.3%; PR-percent of positive nuclei with cutoffs: MM: 83.8% to 99.0%/IA: 85.0% to 99.0%/IA vs. MM: 81.3% to 99.0%, and intensity score: MM: 58.8% to 88.0%/IA: 68.8% to 88.0%/IA vs. MM: 58.8% to 84.0%).

The study results show that Aperio's digital IHC IA solution for ER/PR is substantially equivalent to scoring by MM.