Comparison of estrogen receptor results from pathology reports with results from central laboratory testing

We compared estrogen receptor (ER) assay results abstracted from pathology reports with ER results determined on the same specimens by a central laboratory with an immunohistochemical assay. Paraffin sections were cut from tissue microarrays containing 3093 breast cancer specimens from women enrolled in the Nurses' Health Study, 1851 of which had both pathology reports and tissue available for central laboratory testing. All sections were immunostained for ER at the same time. The original assays were biochemical for 1512 (81.7%) of the 1851 specimens, immunohistochemical for 336 (18.2%), and immunofluorescent for three (0.2%). ER results from pathology reports and repeat central laboratory testing were in agreement for 87.3% of specimens (1615 of the 1851 specimens; kappa statistic = 0.64, P < .001). When the comparison was restricted to the specimens for which the ER assays were originally performed by immunohistochemistry, the agreement rate increased to 92.3% of specimens (310 of the 336 specimens; kappa statistic = 0.78, P < .001). Thus, ER assay results from pathology reports appear to be a reasonable alternative to central laboratory ER testing for large, population-based studies of patients with breast cancer.