A total of 2,718 blood samples were analyzed in five virological laboratories for the presence of cytomegalovirus (CMV) by in-house tests and one standardized plasma PCR assay. Results from in-house tests showed remarkable variability. Detection of CMV pp65 antigen or DNA from cells was more sensitive than that by plasma CMV PCR assay.

Early diagnosis of human cytomegalovirus (HCMV) infection and the introduction of preemptive antiviral therapy have reduced HCMV-related mortality after allogeneic stem cell transplantation. A critical goal remains stratifying risk profiles and minimizing potential harm owing to antiviral overtreatment. We compared the commercially available standardized COBAS Amplicor CMV Monitor (CACM) to an in-house PCR assay, for the monitoring of HCMV infection. Seventy-two patients were surveyed by an in-house PCR of whole blood, quantitative viral load assessment by CACM and virus culture assays in a prospective and a retrospective study. A high concordance between CACM and PCR was documented. The viral load at onset correlated with the peak viral load (Spearman rank correlation R ¼ 0.634, P ¼ 0.0004). In patients developing HCMV disease, both viral loads were in trend higher (P ¼ 0.823, respectively P ¼ 0.053), and the viremic episodes longer (P ¼ 0.015), as compared to asymptomatically HCMV-infected patients. The serological pre-transplant status was the major risk factor for the development of HCMV disease, showing highest risk for seropositive patients receiving a seronegative graft, whereas donor type (related or unrelated) and graft type (bone marrow or peripheral blood mobilized stem cells) did not have an influence. HCMV infection proved to be a risk factor for the development of non-viral opportunistic infections (P ¼ 0.002).

Summary:Preemptive treatment based on the sensitive detection of CMV-DNA has helped to reduce HCMV-related mortality after allogeneic stem cell transplantation (SCT). Detection of active viral replication might help to better predict HCMV disease. In this study, 33 recipients at risk for HCMV infection after allogeneic SCT were prospectively monitored 1؋/week for active HCMV infection by NASBA, whole blood DNA-PCR and virus culture assays. Preemptive antiviral therapy was initiated after the second positive PCR result, while NASBA results were not considered for clinical decision-making. Overall, a high agreement between PCR and NASBA on a per sample (85.3%) and per patient (87.9%) level was demonstrated. HCMV DNA titers in the blood were found to be higher in PCR + /NASBA + compared to PCR + /NASBA ؊ samples (P Ͻ 0.01). None of the NASBA-negative patients developed HCMV disease. Sixteen of 18 patients receiving PCR-based preemptive therapy were also found NASBA positive. There was no difference between the assays for the time to the first positive test result. However, the time to the first negative test result upon initiation of antiviral therapy was significantly shorter for the NASBA assay (P ‫؍‬ 0.002), indicating a high positive predictive value to assess the efficacy of antiviral therapy. Three patients developed late-onset HCMV disease, all of whom were found to be PCR and NASBA positive. In conclusion, the data presented clearly demonstrate the value of patient monitoring using the NASBA assay to early diagnose active HCMV infection and to assess the efficacy of antiviral therapy in high risk patients after allogeneic SCT. A prospective comparison of PCR-based vs NASBAbased preemptive therapy is ongoing.