Monitoring of cytomegalovirus (CMV) infection in solid organ transplant recipients: quantitation of CMV DNAemia by two real-time polymerase chain reaction assays

Background and aim: Quantification of cytomegalovirus (CMV) DNAemia is essential in clinical management of post-transplant infection. We evaluated the performances of two quantitative real-time polymerase chain reaction (PCR) assays.
Materials and Methods: 114 serial whole blood samples collected from 14 actively infected transplant recipients were processed by Abbott RealTime CMV PCR kit (Abbott Molecular) and CMV ELITe MGB™ kit (ELITech Group). The Quality Control for Molecular Diagnostics human CMV panels was also tested.
Results: Sixteen (14%) samples resulted negative and 59 (51.7%) positive with a quantitative result for both assays. In the 59 samples, the coefficient of correlation was 0.856. Bland-Altman analysis showed a mean difference of <0.11 log10 copies/mL (standard deviation=0.38 log10 copies/mL). The assays gave CMV-DNA loads differing by 1 log10 DNA copies/mL in 57 samples (96.6%) and by <0.5 log10 DNA copies/mL in 48 samples (81.3%). Eleven (9.6%) samples were positive with a quantitative result with Abbott and negative with ELITech. Sixteen (14%) positive samples with a quantitative result for Abbott resulted positive but below the lower limit of quantification (LLQ) for ELITech. Twelve (10.5%) samples resulted negative with ELITech and positive but below the LLQ with Abbott. No samples were positive with ELITech and negative with Abbott.
Conclusions: The assays showed a good correlation between CMVDNA levels detected and variation in CMV-DNA <0.5 log10 was observed in the majority of the samples. The viral load kinetic profiles of the assays were overlapping in all patients, but Abbott showed higher sensitivity in samples containing lower amount of DNA. The clinical value of this greater sensitivity requires further investigation.