Comparing BamHI-W and CE-marked assays to detect circulating Epstein-Barr Virus (EBV) DNA of nasopharyngeal cancer patients in a non-endemic area.

OBJECTIVES

Plasma Epstein-Barr Virus (EBV)-DNA is a well-established prognostic biomarker in nasopharyngeal carcinoma (NPC). Different methods for assessment include single-copy gene targeted, European Conformity (CE)-marked assays, which are mostly employed in non-endemic settings, vs multiple-copy gene targeted, in-house BamHI-W based assays, which currently represent the most widely used method for EBV-DNA quantification. To date, evidence concerning the commutability of these different assays is still limited.

MATERIALS AND METHODS

From August 2016 to March 2018, 124 plasma and 124 whole blood (WB) samples from 93 NPC patients were collected at different time-points for each patient. EBV-DNA viral load was quantified in pre- (n = 12) and post-treatment (n = 9), follow-up (n = 53), and recurrent/metastatic (R/M) (n = 50) phase. For each sample, one in-house BamHI-W vs three different CE-marked plasma assays were compared; the performance of plasma vs WB matrix was also assessed. Quantitative agreement of EBV-DNA values was evaluated by linear correlation and Bland-Altman analysis.

RESULTS

A statistically significant (p = 0.0001) agreement between all CE-marked and the BamHI-W assays was found using plasma matrix, regardless of clinical phase. The results obtained in copies/ml were comparable to those expressed in IU/ml. When using WB matrix, the number of positive detections increased in the post-treatment phase.

CONCLUSIONS

Our retrospective comparison supported an agreement between Plasma BamHI-W and CE-marked assays in measuring EBV-DNA for non-endemic NPC patients. There were no significant interferences from different measurement units (IU/ml vs copies/ml). Further evaluations are needed to better clarify the role of WB.