Comparison of immunoperoxidase and DNA in situ hybridization techniques in the diagnosis of cytomegalovirus colitis.

Cytomegalovirus (CMV) infection of the colon occurs in immunocompromised patients and in patients with ulcerative colitis. In the former, it can cause serious bleeding or colonic perforation and in the latter, it may precipitate a fulminant phase of illness. The authors compared the immunoperoxidase technique with a monoclonal antibody (Mab) against CMV early antigen and DNA in situ hybridization using a biotinylated probe in the identification of virus-infected cells in colon samples from patients with known CMV colitis and with fulminant ulcerative colitis without histologic evidence of infection. The Mab stained the nuclei of infected cells without recognizable viral inclusions particularly in cases showing few characteristic viral inclusions. In well-developed CMV infections, with many inclusions, immunoperoxidase staining was less prominent. The biotinylated DNA probe recognized cytopathic cells with prominent inclusions but was only rarely positive in smaller cells. In specimens with few inclusions, there was no staining with in situ hybridization. No positivity was observed by either technique in cases of fulminant ulcerative colitis with no morphologic evidence of CMV infection. The authors conclude that immunoperoxidase using monoclonal anti-CMV early antigen adds useful information in the evaluation of early or focal cases of CMV colitis. DNA in situ hybridization is usually positive in cytopathic cells and is less useful for diagnosis. CMV could not be demonstrated in cases of fulminant ulcerative colitis when viral inclusions were not observed in routine preparations.