Validity and Reproducibility of Immunohistochemical Scoring by Trained Non-Pathologists on Tissue Microarrays
Josien C.A. Jenniskens, Kelly Offermans, Iryna Samarska, Gregorio E. Fazzi, Colinda C.J.M. Simons, Kim M. Smits, Leo J. Schouten, Matty P. Weijenberg, Piet A. van den Brandt, Heike I. Grabsch
Abstract
Abstract Background: Scoring of immunohistochemistry (IHC) staining is often done by non-pathologists, especially in large-scale tissue microarray (TMA)-based studies. Studies on the validity and reproducibility of scoring results from non-pathologists are limited. Therefore, our main aim was to assess interobserver agreement between trained non-pathologists and an experienced histopathologist for three IHC markers with different subcellular localization (nucleus/membrane/cytoplasm). Methods: Three non-pathologists were trained in recognizing adenocarcinoma and IHC scoring by a senior histopathologist. Kappa statistics were used to analyze interobserver and intraobserver agreement for 6,249 TMA cores from a colorectal cancer series. Results: Interobserver agreement between non-pathologists (independently scored) and the histopathologist was “substantial” for nuclear and membranous IHC markers (κrange = 0.67–0.75 and κrange = 0.61–0.69, respectively), and “moderate” for the cytoplasmic IHC marker (κrange = 0.43–0.57). Scores of the three non-pathologists were also combined into a “combination score” (if at least two non-pathologists independently assigned the same score to a core, this was the combination score). This increased agreement with the pathologist (κnuclear = 0.74; κmembranous = 0.73; κcytopasmic = 0.57). Interobserver agreement between non-pathologists was “substantial” (κnuclear = 0.78; κmembranous = 0.72; κcytopasmic = 0.61). Intraobserver agreement of non-pathologists was “substantial” to “almost perfect” (κnuclear,range = 0.83–0.87; κmembranous,range = 0.75–0.82; κcytopasmic = 0.69). Overall, agreement was lowest for the cytoplasmic IHC marker. Conclusions: This study shows that adequately trained non-pathologists are able to generate reproducible IHC scoring results, that are similar to those of an experienced histopathologist. A combination score of at least two non-pathologists yielded optimal results. Impact: Non-pathologists can generate reproducible IHC results after appropriate training, making analyses of large-scale molecular pathological epidemiology studies feasible within an acceptable time frame.