Comparison of real-time PCR and pp65 antigen assays for monitoring the development of Cytomegalovirus disease in recipients of solid organ and bone marrow transplants

Cytomegalovirus (CMV) infection is a frequent complication in transplant recipients. This retrospective study compared real-time PCR (rt-PCR) and a pp65 antigen assay as tools for monitoring CMV infection in solid organ (SOT) and bone marrow (SCT) transplant patients. The study tested 2662 samples by rt-PCR, and 1284 specimens with a pp65 antigen assay. 24.3% of the rt-PCR samples and 4.1% of the pp65 antigen samples were positive. 793 specimens, from 230 patients, were tested with both assays. In 6.7% of samples, both tests were positive; in 72.7% both were negative; in the remaining 20.6% of cases, the results were discordant. CMV disease was diagnosed in 50 patients. Results from the two methods were poorly correlated (r=0.460). The sensitivity of rt-PCR (94%) was higher than that of the pp65 antigen assay (27%). Both assays showed high specificity (92% and 99%, respectively). ROC curve analysis, performed separately for SOT and SCT patients, confirmed that rt-PCR outperformed the pp65 assay in the detection of CMV. These findings provide evidence that rt-PCR is a reliable diagnostic tool, and that it can be more effective than pp65 based assays in monitoring CMV infection progression and in guiding therapy in immunocompromised patients.