Quantitative PCR is faster, more objective and more reliable than immunohistochemistry for the diagnosis of Cytomegalovirus Gastrointestinal disease in allogeneic stem cell transplantation

Abstract Diagnosis of gastrointestinal (GI) cytomegalovirus (CMV) disease relies both on the presence of GI symptoms and detection of CMV, mainly by immunohistochemistry (IHC), in GI biopsy specimens. Thus in a symptomatic patient, a positive CMV-IHC result is accepted as a diagnosis of CMV disease. However, a positive CMV-PCR in GI tissue is considered “possible” CMV disease. Therefore, it would be very useful if, in practice, both techniques showed equal sensitivity and reliability. This is because PCR has many practical advantages over IHC for detecting CMV. The aim of this study was to compare quantitative PCR with IHC for diagnosis of GI CMV disease. A total of 186 endoscopic GI biopsy specimens from 123 patients with GI symptoms after an allogeneic stem cell transplantation (allo-SCT; 2004–2017) were analyzed by IHC and PCR on 113 paraffin-embedded and on 73 fresh samples. The results were then compared. Results All patients with macroscopic lesions in the mucosa and CMV-IHC+ biopsy specimens (e.g., “proven” CMV disease, n=28), all but one were CMV-PCR+. Of the patients without macroscopic lesions in the mucosa and CMV-IHC+ biopsy (e.g., “probable” CMV disease, n=4), only one was CMV-PCR+. Eight patients had CMV-IHC-/CMV-PCR+ gut biopsies. These cases fall within the current definition of “possible” CMV disease. In six of these eight cases (75%), the viral load in GI tissue was very high (>10,000 c/µg). Taken together, the results from the “proven” and “probable” cases revealed that CMV-PCR shows the same sensitivity (100%), specificity (98%) and positive (93%) and negative predictive value (100%) than CMV-IHC. Conclusion Detection of CMV in fresh GI mucosa by quantitative PCR is as useful as IHC for diagnosis of GI CMV disease. The results show that quantitative PCR has the same sensitivity, specificity and positive/negative predictive value than IHC.