Study on sero-diagnosis of nasopharyngeal carcinoma using a dual antibody test against recombinant Epstein-Barr virus antigens.

Background & Objective: The aim of this study was to optimize a dual-antibody assay for sero-diagnosis of nasopharyngeal carcinoma(NPC) by evaluating 4 Epstein-Barr virus(EBV) antigen-based enzyme-linked immunosorbent assays(ELISAs).
Methods: The serum samples of 57 pretreated NPC patients and 58 apparently healthy adults in Guangzhou were collected. The levels of anti-EBV antibody in the sera were tested by 4 ELISAs, which were developed using fusion proteins of glutathione transferase and EBV specific recombinant antigens, namely, EBNA1-IgA, EBNA1-IgG, Zta-IgA, and Zta-IgG.
Results: When evaluated individually, the sensitivity(0.9123) and negative predictive value(0.9074) of EBNA1-IgA were the highest among the 4 ELISAs tested. Zta-IgA test had the highest individual accuracy rate(pi, 0.8870) and Youden index(J, 0.7738). The dual positives for EBNA1-IgA and Zta-IgA were the highest among the 4 dual positives when paired ELISAs were evaluated. Five NPC patients with negative reaction to EBNA1-IgA showed positive reaction of Zta-IgA, and 7 NPC patients with negative reaction to Zta-IgA showed positive reaction of EBNA1-IgA.
Conclusion: The EBNA1-IgA assay is more suitable than the other 3 ELISAs(EBNA1-IgG, Zta-IgA, and Zta-IgG) when used individually for serological diagnosis of NPC. When two assays are combined, EBNA1-IgA and Zta-IgA have complementary effect on serological diagnosis for NPC and is thus an optimal combination of serum antibody assays.