Preemptive therapy (PET) is safe and effective in controlling Cytomegalovirus (CMV) infection after pediatric liver transplantation (LT) and allows to observe the kinetics of quantitative CMV-DNA viral load till it reaches the treatment thresholds. While early detection of low-to-moderate CMV-DNA levels may not indicate active viral replication, awaiting the viral load to exceed the treatment threshold may lead to viremic breakthroughs and CMV disease. We assessed the capacity of quantitative CMV-RNA (UL21.5 mRNA) to identify active viral replication and its accuracy in identifying clinically significant CMV infection (csCMVi) needing PET in LT children. One-hundred and forty-four comparative quantitative CMV-RNA and CMV-DNA determinations were obtained from 12 children followed prospectically for 6 months after LT. Of 52 CMV-DNA-positive specimens, 17 (32%) were also CMV-RNA-positive, while CMV-RNA was undetectable in CMV-DNA-negative specimens. All children with csCMVi had early detectable CMV-RNA, peaking simultaneously to CMV-DNA (median CMV-DNA: 65 906 cp/mL; median CMV-RNA: 767 cp/mL); conversely, none of those with persistently low DNAemia proved CMV-RNA-positive. In this first pilot study, CMV-RNA had 100% sensitivity and specificity in identifying children needing PET after pediatric LT. The early detection of CMV-RNA marks significant CMV infection/reactivation, thus allowing to avoid unnecessary antiviral treatment.
