Immunohistochemistry Stain or Assay

Course overview

Since its inception, immunohistochemistry (IHC) has been called a stain principally because of its origin as a byproduct of traditional histochemistry. Simply, a tool to identify specific targets in cells and tissues that could not be distinguished by traditional morphologic or histochemical techniques. There is a great deal of controversy surrounding this notion. A recent editorial by B. Magnani and C. Taylor has brought the issue back to forefront of the histopathology community. Over the last 25 years, IHC has evolved into a complex testing modality. IHC has developed into a test that requires both qualitative AND quantitative interpretation, ushering in the era of companion diagnostics. Unfortunately, IHC test quality assurance is still grounded in subjective pass/fail interpretation based on non-standardized control tissues that are insensitive and irreproducible. The major obstacle has been the lack of appropriate tools to assess assay performance during the analytical phase, similar to what is done in clinical pathology laboratories. However, IHC calibration technology is now available that can establish analytical standardization that will help address both interpretive and technical errors, perhaps providing a means to better understand pre- and post-analytical phases. This presentation will introduce the concept of analytical reference standards for immunohistochemistry, provide some examples of the different technology as well as examples of their use.