An overview of infectious disease laboratory methods: an update for the histopathologist

Abstract

The histopathologist plays a crucial role in the diagnosis of infectious diseases. In some cases they are the first to highlight the presence of an infection where one was not initially suspected. Collaboration with other specialities is a key part of the histopathologist's work, though specialist knowledge of infectious disease pathology remains a niche area for many. The field of infectious disease diagnostics has undergone tremendous change over the past four decades, while maintaining methods developed by the pioneers of microbiology a century ago. This review will start with an outline of the key methodologies of microscopy, culture, serology, fungal antigen testing, and molecular techniques. The second part will focus on particular histopathological findings and their associated infections. The examples provided are representative of scenarios encountered in our practice in the United Kingdom. We include examples of the diagnostic workup of granulomatous inflammation, sulphur granules containing filamentous bacteria and viral cytopathic effects. The possibilities for PCR testing on fixed formalin paraffin embedded tissues is discussed. This review provides a foundation for histopathology trainees and specialists to strengthen their knowledge of infection diagnostics.