A Comparison of CMV Detection in Gastrointestinal Mucosal Biopsies Using Immunohistochemistry and PCR Performed on Formalin-fixed, Paraffin-embedded Tissue

Cytomegalovirus (CMV) can precipitate and exacerbate gastrointestinal (GI) mucosal injury. The gold standard for CMV detection in formalin-fixed, paraffin-embedded (FFPE) tissue is immunohistochemistry (IHC). Although CMV polymerase chain reaction (PCR) on fresh tissue may be a valuable adjunct to IHC, its utility is unknown for FFPE tissues. We therefore evaluated quantitative, real-time CMV PCR in a total of 102 FFPE GI biopsy specimens from 74 patients with a history of hematopoietic stem cell or solid organ transplant, inflammatory bowel disease, human immunodeficiency virus infection, or unspecified colitis. CMV DNA was detected by PCR in 90.9% (30/33) of IHC-positive, 14.5% (8/55) of IHC-negative, and 20.0% (1/5) of IHC-equivocal FFPE tissues. Quantitation of CMV DNA copies normalized to beta-globin demonstrated a wide range of values (median 0.276; range, 0.0004 to 144.50). Importantly, 93.3% (14/15) of patients with IHC-positive, active colitis showed no evidence of CMV in matched concurrent, histologically normal biopsies tested by PCR. These results suggest that CMV PCR on FFPE GI biopsies complements IHC and has the potential to identify additional patients who may benefit from anti-CMV therapy.