Standardization in immunohistochemistry.

Over the last few years, the role of immunohistochemical analysis has been changing from that of an ancillary diagnostic technique to that of a stand-alone diagnostic method, the results of which determine treatment approach. With this change comes a need for increasing standardization of both preanalytical and analytical methods, so that results emanating from different laboratories are directly comparable. These efforts have been aided to some degree by the development of automated staining systems and by the increased use of test kits, but interlaboratory reproducibility for immunohistochemical methods is still far lower than that of most clinical analytical measurements. In this article, the author presents some approaches to further reduce intra- and interlaboratory variation in the performance of immunohistochemical assays, focusing attention on guidelines recently published by NCCLS.