Quantitation of cytomegalovirus DNA by real-time polymerase chain reaction in peripheral blood specimens of patients with solid organ transplants: comparison with end-point PCR and pp65 antigen test.

The polymerase chain reaction (PCR) for cytomegalovirus (CMV) DNA quantitation provides sensitive and specific data for detecting CMV as well as monitoring the infection and determining the appropriate antiviral strategy. A recently introduced real-time PCR assay for CMV DNA quantitation was applied on 158 peripheral blood leukocytes (PBLs) from 32 liver-transplanted patients with CMV asymptomatic infection and correlated with a commercial quantitative end-point PCR (COBAS AMPLICOR CMV Monitor) and CMV pp65 antigenemia. A good correlation was found between real-time PCR and pp65 antigen test (r2 = 0.691) and the two PCR assays (r2 = 0.761). Real-time PCR data were higher in pre-emptive treated patients (>20 pp65 + positive cells, median CMV DNA value: 3.8 log(10) copies/500,000 PBLs) than in not-treated ones (2.9 logs). According to pp65 levels of 0, 1-10, 11-20, 21-50, 51-100, and >100 positive cells/200,000 PBLs, median CMV DNA by real-time PCR was 2.6, 3.0, 3.6, 4.0, 4.2, and 4.8 logs, respectively, (CMV DNA levels by COBAS AMPLICOR: 2.8, 2.9, 3.8, 3.7, 3.9, and 4.0 logs). For samples with >20 pp65 + cells, real-time PCR gave significantly higher values than in groups with <20 pp65 + cells, whereas the COBAS AMPLICOR results showed a slower progression rate. Dilutions of CMV AD169 strain were used to probe real-time PCR reproducibility (between and intra-assay variability <2%) and sensitivity (100% detection rate at 10 copies/reaction, 28.5% with end-point PCR). In conclusion, real-time PCR significantly improves the study of CMV DNA dynamics due to a more reliable quantitation of CMV DNA for moderate and high DNA level compared to end-point PCR with better sensitivity and specificity. Real-time PCR provides more precise information for evaluating infection progress and assessing antiviral response, simplifying and accelerating the process of producing a reliable quantitation of CMV DNA for clinical purposes.