Background: Serum immunoglobulin A antibodies against Epstein–Barr virus(EBV), viral capsid antigen(VCA?Ig A) and early antigen(EA?Ig A), are used to screen for nasopharyngeal carcinoma(NPC) in endemic areas. However, their routine use has been questioned because of a lack of specificity. This study aimed to determine the distributions of different subtypes of antibody and to illustrate how the natural variation patterns affect the specificity of screening in non?NPC participants.Methods: The distribution of baseline VCA?IgA was analyzed between sexes and across 10?year age groups in 18,286 non?NPC participants using Chi square tests. Fluctuations in the VCA?IgA level were assessed in 1056 non?NPC participants with at least two retests in the first 5?year period(1987–1992) after the initial screening using the Kaplan–Meier method.Results: The titers of VCA?Ig A increased with age(P < 0.001). Using a previous serological definition of high NPC risk, nasopharyngeal endoscopy and/or nasopharyngeal biopsy would be recommended in 55.5% of the non?NPC partici?pants with an initial VCA?Ig A?positive status and in 20.6% with an initial negative status during the 5?year follow?up. However, seroconversions were common; 85.2% of the participants with a VCA?Ig A?positive status at baseline con?verted to negative, and all VCA?Ig A?negative participants changed to positive at least once during the 5?year follow?up. The EA?Ig A status had a high seroconversion probability(100%) from positive to negative; however, it had a low probability(19.6%) from negative to positive.Conclusions: Age? and sex?specific cutoff titer values for serum anti?EBV antibodies as well as their specific titer fluc?tuation patterns should be considered when defining high NPC risk criteria for follow?up diagnostics and monitoring. Background: Serum immunoglobulin A antibodies against Epstein-Barr virus (EBV), viral capsid antigen (VCA IgA) and early antigen (EA IgA), are used to screen for nasopharyngeal carcinoma (NPC) their routine use has been questioned because of lack of specificity. This study aimed to determine the distributions of different subtypes of antibody and to illustrate how the natural variation patterns affect the specificity of screening in non? NPC participants. Methods: The distribution of baseline VCA? IgA was analyzed between sexes and across 10? Year age groups in 18,286 non? NPC participants using Chi square tests. Fluctuations in the VCA? IgA level were assessed in 1056 non? NPC participants with at least two retests in the first 5? year (1987-1992) after the initial screening using the Kaplan-Meier method. Results: The titers of VCA-Ig A increased with age (P <0.001). Using a previous serological definition of high NPC risk, nasopharyngeal endoscopy and / or Nasopharyngeal biopsy would be recommended in 55.5% of the non? NPC partici? pants with an initial VCA? Ig A? positive status and in 20.6% with an initial negative status during the 5? year follow? up. However, seroconversions were common; 85.2% of the participants with a VCA? Ig A? Positive status at baseline con? Verted to negative, and all VCA? Ig A? Negative participants changed to positive at least once during the 5? Year follow? Up. The EA? Ig However, it had a low probability (19.6%) from negative to positive. Conclusions: Age? And sex? Specific cutoff titer values ​​for serum anti? EBV antibodies as well as their specific titer fluc? tuation patterns should be considered when defining high NPC risk criteria for follow? up diagnostics and monitoring.