Qualitative plasma PCR assay (AMPLICOR CMV test) versus pp65 antigenemia assay for monitoring cytomegalovirus viremia and guiding preemptive ganciclovir therapy in allogeneic stem cell transplantation

The performances of a commercially available qualitative plasma PCR assay ( AMPLICOR CMV test; Roche Diagnostics) and the pp65 antigenemia assay (AG) w ere evaluated for the monitoring of cytomegalovirus (CMV) viremia in 43 all ogeneic stem cell transplant recipients. In addition, the suitabilities of both assays for triggering the initiation of preemptive ganciclovir therapy were assessed. A total of 37 CMV viremic episodes were detected in 28 pati ents. Positivity of plasma PCR testing in one or more consecutive specimens was the only marker of CMV viremia in 18 of the 37 episodes (PCR positive and AG negative, n = 50 specimens). Five episodes were diagnosed on the bas is of a single positive AG result (AG positive and PCR negative, n = 5 spec imens); both assays were eventually positive (PCR positive and AG positive, n = 27 specimens) for 14 viremic episodes; for these episodes, conversion of the PCR assay result to a positive result occurred an average of 1 week before conversion of the AG result. Overall, the concordance between the tw o methods was 90%, and the sensitivities of the plasma PCR assay and AG for the detection of CMV viremic episodes were 86.5 and 51.3%, respectively. T wo patients who tested positive by both assays simultaneously progressed to CMV end-stage organ disease, despite the initiation of preemptive ganciclo vir therapy. Conversion of the AG result to a negative result upon administ ration of preemptive ganciclovir therapy occurred a median of 7.5 days earl ier than conversion of the plasma PCR assay result. Nineteen of the 28 pati ents with CMV viremia received AG-guided preemptive ganciclovir therapy; ha d the positivity of the plasma PCR assay triggered the initiation of preemp tive therapy, 9 additional patients would have been unnecessarily treated s ince none of them developed CMV end-stage organ disease. Although the AMPLI COR CMV assay is more sensitive than AG, the latter appears to be more suit able both for guiding the initiation of preemptive therapy and for monitori ng a patient's response to antiviral therapy.