Multicenter quality control study for human cytomegalovirus DNAemia quantification

Standardized protocols and methods for virological monitoring are mandatory for the correct surveillance of human cytomegalovirus (HCMV) infection in transplanted patients receiving pre-emptive therapy. Fifteen Italian viral diagnostic laboratories belonging to different transplantation centers participated in the external Quality Control Programme for Molecular Diagnostics of HCMV-DNA by using two in-house and five commercial methods for HCMV-DNA quantification. The different methods shared 100% specificity, and sensitivity reached 100% when samples containing > 1,000 copies/ml were considered. The variability range was wide (about 2 log 10) for samples containing a lower amount of HCMV-DNA (< 1,000 copies/ml), but it decreased with increasing concentrations of HCMV-DNA. For HCMV-DNA levels ≥5,000 copies/ml, the different methods provided results within a ±0.5 log 10 variability range, while the 80% range (range in which 80% of results obtained will fall) was within ±0.3 log 10 or less. An acceptable level of variability was reached among different in-house and commercial methods for HCMV-DNA quantification in samples containing a clinically significant viral DNA amount. Based on these data, standardized cutoffs established for pre-emptive therapy in different transplantation centers should provide comparable clinical and virological results among centers.