Monitoring of leukocyte cytomegalovirus DNA in bone marrow transplant recipients by nested PCR.

A nested PCR assay for the detection of human cytomegalovirus (CMV) DNA was evaluated by weekly monitoring of blood samples taken from 101 bone marrow transplant (BMT) recipients. When peripheral blood leukocytes were used as the source of CMV DNA, even a modified assay with stringent temperature-cycling conditions was as sensitive as the standard assay. The sensitivity, specificity, and positive predictive value of two consecutively positive leukocytic PCR results with this modified assay in predicting CMV disease of 101 patients submitting 1,441 peripheral blood leukocyte samples were found to be 92.1, 63.5, and 60.3%, respectively. The positive predictive value of patients' seropositivity for CMV was 40%, while that of viremia was 72%. However, viremia followed CMV disease by a median of 1.5 days, while the first leukocytic positive PCR assay preceded disease by a median of 14 days. By use of the criteria of two consecutively positive PCR results instead of recipient CMV seropositivity for starting preemptive ganciclovir treatment, 38 of the 43 recipients with isolated single positive or negative assays (groups I and II) would be spared unnecessary ganciclovir treatment. Moreover, two other findings support the use of antiviral prophylaxis before engraftment in high-risk cases and subsequent preemptive treatment of patients with two consecutively positive PCR assays. First, for 7.9% of 76 patients with positive assays (groups II and III), the first positive PCR assay occurred before engraftment, which implied the presence of viral DNA in the blood (DNAemia) soon after transplantation. Second, isolated single positive assays which were clustered around the second to sixth weeks after transplantation were found for 18 patients (group II) and could represent abortive episodes of CMV infection.