Epstein–Barr virus (EBV) is a member of the Herpesviridae family of viruses. Following primary infection that may occur early in childhood or adolescence, EBV establishes latency primarily in B- cells and in epithelial cells [1,2]. In patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) and other cancer treatment resulting in immune suppression, reactivation of latent EBV infections occurs frequently and in some cases could result in post-transplant lymphoproliferative disorder (PTLDs) [3]. The risk of developing PTLD is highest within the first year post-transplant and hence monitoring of EBV is particularly important in this patient population [4].

Monitoring of EBV reactivation is routinely performed using quantitative nucleic acids amplification tests (NATs) including quantitative real-time PCRs to measure EBV DNA concentration as a proxy for EBV viral loads. Until recently, quantitative EBV PCRs were all laboratory-developed tests (LDTs), performed on either whole blood, serum, plasma or peripheral blood mononuclear cells (PBMC). In addition to variation in sample types, LDTs varied in platforms used to perform DNA extraction and amplification, the EBV gene target as well as the calibrators and standard used to quantify the viral loads [5]. Given these multiple sources of variability, comparison of EBV viral loads obtained across different laboratories has been a significant challenge [6]. To minimize this variability, in 2011, the 1st World health Organization (WHO) International standards for EBV were developed and became available for calibration of secondary reference materials to international unit (IU). In one study, the use of the EBV WHO standards to convert viral loads from copies/mL to IU/mL resulted in lower EBV values and reduced, but did not eliminate, variability in viral load measurements [7].

A potential solution to improving the standardization of EBV viral loads is increasing the number of commercially available Food and Drug Administration (FDA)-approved tests performed on systems requiring minimal sample manipulation with results calibrated to the WHO standards [8]. In 2020, the Cobas EBV test (Roche Molecular Systems, Inc., Pleasanton, CA), an in vitro nucleic acid amplification test, received De Novo approval FDA approval for the quantitation of EBV DNA in plasma samples of transplants patients on the cobas 6800/8800 Systems. The Cobas EBV test is a dual target test that includes automated specimen preparation and DNA extraction followed by PCR amplification, detection and quantitation of EBV DNA in IU/mL. The Cobas EBV test is the first FDA-cleared assay for monitoring of EBV viral loads.

The goal of this study was to compare the EBV viral loads obtained with the new Cobas EBV test to those obtained with an EBV LDT in a HSCT patient population at Memorial Sloan Kettering Cancer Center (MSK).