The Positive Immunohistochemical Staining of Cytomegalovirus in Colon Biopsy Samples Suggests That the Viral DNA Load in qPCR Is High

Background and Aim Immunohistochemistry (IHC) and/or polymerase chain reaction (PCR) are essential for confirming active cytomegalovirus (CMV) infection in patients with inflammatory bowel disease (IBD). A definitive cut-off has not yet been established; however, Roblin et al suggested a viral load threshold of > 250 viral copies/mg of tissue. In this study, we examined the concordance between IHC and quantitative real-time PCR (qPCR) in the detection of CMV in colonic biopsy specimens. Methods A total of 170 samples that underwent IHC and qPCR were collected. The positive rate and concordance of IHC and qPCR were studied, and the impact of ulcer tissue on both detection methods was observed. Results In a study of 170 hematoxylin-eosin (H&E) sections, 8 samples were found to be infected with cytomegalovirus. The positive rates of CMV detection using IHC and qPCR were 17% (29/170) and 25% (43/170), respectively. Among the IHC-positive samples, the qPCR positive rate was 100% (29/29), with all CMV-DNA loads > 250 copies/mg. The concordance between IHC and qPCR was 94% (kappa = 0.756, P < .001). IHC analysis revealed that positive cells in ulcerated mucosa were more frequent than those in nonulcerated mucosa ( P < .001). Additionally, a total of 14 samples tested negative for CMV via IHC but positive through qPCR. Among these, 11 samples did not contain ulcerated tissue. Conclusion The presence of one or more IHC-positive cells in colon biopsy samples indicates a high CMV-DNA load in qPCR (> 250 copies/mg). IHC-positive cells were more frequently observed in ulcerated mucosa compared to nonulcerated mucosa.