Influence of the 1st International WHO EBV Standard on quantitation of Epstein-Barr virus viral load in serum samples

Abstract

Objectives: The aim of this study was to evaluate the impact of normalization with 1<sup>st</sup> International WHO Standard for Epstein-Barr Virus (EBV) on EBV DNA quantitation in 90 clinical serum samples obtained from hematopoietic stem cells transplant recipients. Methods: EBV DNA loads (EDLs) obtained with the use of six different commercially available and in-house developed assays, including various automated DNA extraction systems, real-time PCR tests and cyclers were compared, both before and after recalculation with conversion factors obtained with 1st International WHO Standard for Epstein-Barr Virus Results: None of six methods was able to detect EBV DNA in all 80 serum samples identified previously as positive but the most effective method turned out to be combination of MagnaPure, LC2.0 and EBV QK (sensitivity 90%). Conversion factors for compared assays, obtained with the WHO standards ranged from 0.998 (MagnaPure/LC2.0/EBV QK) to 1.138 (MagnaPure/LC2.0/<I>In house</I>). In two out of four comparisons, differences in the average EDLs, initially significant, have changed to statistically not significant after conversion to IU/mL. Conclusions: Positive impact of EDLs standardization was shown, resulting in lower discrepancies between average values obtained with various methods. Method-to-method variability was lower for samples with a higher EDLs (>3.5 log), regardless the units used. Results showed the advantage of certain commercial methods over “in-house” method.