Multicenter comparative study of Epstein-Barr virus DNA quantification for virological monitoring in transplanted patients

Background: EBV-related post-transplant lymphoproliferative diseases are usually accompanied by increased EBV DNA in peripheral blood. Monitoring EBV DNAemia is the basis for weighing decisions regarding initiation of pre-emptive or anti-EBV-related tumor therapy. However, the definition of clinically relevant cut-off values is hampered by the lack of standardization in EBV DNA testing. Objectives: To estimate inter-laboratory variability and to evaluate the impact of different matrices in EBV DNA load determination in Italian laboratories involved in monitoring of virus infections in transplanted patients. Study design: Two different proficiency panels were distributed among seven centers: the first contained cell-associated and cell-free EBVs; the second was prepared by spiking both cell-associated and cell-free EBVs in EBV DNA-negative whole blood from EBV seropositive healthy donors. Samples were extracted and amplified with different methods. Intra-laboratory and inter-laboratory variabilities was evaluated. Results: 337 EBV DNA determinations were performed. Sensitivity was 100% for both panels, specificity was 100% for the first and 74% for the second panel, where whole blood was utilized as the matrix. Discrepant results in the second panel were restricted to samples containing low copy numbers. Quantification fell within ±0.5 log in 73% of the determinations. Values for cell-associated samples tended to be more heterogeneous than those obtained from cell-free samples. Good overall linearity was observed for each sample type; inter-laboratory variability ranged from 4.71% to 12.86%. Conclusions: The results of this multicenter study indicate that EBV DNAemia may be reliably quantified by different laboratories using a variety of commercial and in-house molecular assays.