Detection of SARS-CoV-2 in tissue: the comparative roles of RT-qPCR, in situ RNA hybridization, and immunohistochemistry.

The emergence of SARS-CoV-2, the causative agent the COVID-19 pandemic, has led to a rapidly expanding arsenal of molecular diagnostic assays for the detection of viral material in tissue specimens. We review the value and shortcomings of available tissue-based assays for SARS-CoV-2 detection in formalin-fixed paraffin-embedded (FFPE) tissue, including immunohistochemistry, in situ hybridization, and quantitative reverse transcription PCR (RT-qPCR). The validation, accuracy, and comparative utility of each method is discussed. Subsequently, we identify commercially available antibodies which render the greatest specificity and reproducibility of staining in FFPE specimens. We offer expert opinion on the efficacy of such techniques and guidance for future implementation, both clinical and experimental.