Diagnostic Value of Epstein-Barr Virus Immunofluorescence and Enzyme-Immunoassay Platforms for Detecting IgA Antibodies in Nasopharyngeal Carcinoma in the Singaporean Cohort.

Epstein-Barr virus (EBV) is well established as the cause of nasopharyngeal carcinoma (NPC), which is prevalent in China and Southeast Asia. Immunofluorescent assays (IFA) for detecting IgA have played an important role in surveillance for early detection of NPC in high-risk groups. However, enzyme-linked immunosorbent assays (ELISA) are increasingly favoured for the higher throughput and interpretation ease. In this study, we compare the performance of both methods comprising 9 EBV IgA kits, using 100 samples from NPC patients and 100 samples from patients who remained NPC-free at follow-up of at least 2 years. Using manufacturer cutoffs, IFA were more sensitive (96%-98%) than ELISA (56%-63%) in the detection of EBV-early antigen (EA) IgA. Both methods had similar specificity (range 95%-100%). Similarly, IFA were also more sensitive (99%-100%), but had lower specificity (48%-81%), in the detection of viral capsid antigen (VCA) IgA than ELISA (sensitivity: 19%-72%; specificity: 73%-94%). However, optimisation of assay cutoff based on receiver operating characteristic (ROC) curves improved the diagnostic accuracy of IFA-VCA IgA kits and ELISA-EA & VCA IgA kits. Overall, IFA demonstrated superior performance to ELISA regardless of the IgA target detected: IFA-EA kits had area under curve (AUC) values of 0.975-0.985 vs. ELISA-EA AUC = 0.873-0.989, and IFA-VCA AUC = 0.961-0.978 vs. ELISA-VCA AUC = 0.748-0.777. Contrary to other publications, IFA was more sensitive than ELISA in the detection of EA and VCA-IgA in our local context. Despite being more laborious with lower throughput, IFA plays a crucial role in NPC screening.