Immunohistochemistry and quantitative analysis of protein expression.

CONTEXT: Immunohistochemistry has taken a central role in the field of pathology, and its role is destined to increase as companion diagnostics analogous to the HercepTest are required for new targeted therapeutics. However, the inherent subjectivity of the assessment of an objective value (the in situ protein concentration) suggests that new technologies to measure the protein concentration may be required to achieve the accuracy required for companion diagnostics. OBJECTIVE: This article discusses the state of immunohistochemistry and reviews the currently available devices for quantitative in situ assessment of protein expression. DATA SOURCES: Data for this work were collected from the published literature, the Internet, and from information provided by device vendors. CONCLUSIONS: Although there is a long history of efforts to quantify immunohistochemistry, there has been a lack of broad acceptance because the resultant objective accuracy has not significantly improved outcome measures compared with the traditional, conventional analysis by eye. As the demand grows for companion diagnostics with complex assessment requirements, we are likely to see increased usage of quantitative platforms, especially those with the capacity to do multiplexed analysis. This most likely will be driven by a requirement for outcomes that cannot be achieved by traditional methods.