ABSTRACT Southeast Asian and immigrant Chinese communities across the globe have disproportionately high NPC incidence, averaging 25-30 times higher than the general population in neighboring areas. EBV infection is extremely common and more than 95% of adults have seroconverted, but only a subset of chronic carriers will develop EBV-associated nasopharyngeal carcinoma (NPC). Latent and clonal EBV infection occurs in the tumor cells, and a variant of a key EBV protein (EBNA1 Val487) required for co-infection with the host has been identified as a cancer risk-variant because it is found in nearly all (98.8%) NPC tumors from NPC-endemic areas. Both EBV serology and EBV DNA sequencing are informative. Early detection screening programs by one of two screening methods (IgA serology, or next-gen sequencing of plasma cell-free EBV DNA) have been recommended for NPC-endemic populations. However, the screening time-interval for routine early detection is not known. A biomarker that can identify high-risk individuals several years before clinical onset would greatly benefit from an early detection screening program. Antibodies to EBV proteins rise several years before NPC onset. IgA serology is a sentinel for aberrant EBV infection at mucosal sites. We previously surveyed EBV IgA/IgG/IgM serology from the serum of incident NPC cases in a Singapore prospective cohort (discovery cohort) and tested the leading biomarker (EBNA1 IgA) in an additional validation cohort from Shanghai, China. The sojourn time for the custom EBNA1 IgA assay was 4 years before NPC diagnosis (100% sensitivity, 100% specificity in 20 case-controls). False-positives emerged in the expanded control samples which is likely attributed to periodic EBV reactivation but background signal could be minimized by removing cross-reactive epitopes yielding a satisfactory EBNA1 IgA assay (93.7% specificity at 100% sensitivity). Following on from the case-control study performed on a low-throughput but highly accurate multiplex immunoblot assay, the goal of this proposal is to develop a high-throughput EBNA1 IgA assay using a prototypic slot blot assay and applying the principles from EBNA1 mapping studies. By leveraging EBV serology, this work is expected to produce a high-throughput assay for NPC risk assessment. Identified high-risk individuals would benefit from an NPC early detection screening program and/or clinical follow-up.