[Comparison of incidence of nasopharyngeal carcinoma in populations with different fluctuation modes of immunoglobulin A antibody levels against Epstein-Barr virus capsid antigen].

Objective: To explore the incidence regularity in populations with different fluctuation modes of Epstein-Barr virus (EBV) antibody levels.
Methods: Based on the data of a NPC mass screening for nasopharyngeal carcinoma (NPC) in Jianggu town and Didou town of Sihui city, Guangdong province from 1992 to 1998, 586 subjects who were positive and retested for twice or above were divided into ascending group (114 subjects), stable or fluctuating group (313 subjects), and descending group (159 subjects) according to the fluctuation of immunoglobulin A antibody against EBV capsid antigen (VCA-IgA) level; 9889 subjects who were negative in the first test of VCA-IgA were set as control group. All the participants were followed-up till December 31, 2007. The incidence, onset time and clinical characteristics of NPC were compared among groups.
Results: The 5-year cumulative detection rates of ascending, stable or fluctuating, and descending group were 3.51% (4/114), 0.64% (2/313) and 0.00% (0/159), respectively; the 5-year cumulative detection proportions were 4/4, 2/6 and 0/2, respectively. Comparing to the control group, the hazard ratio (HR) for the incidence of NPC in ascending group was highest (HR = 10.96, 95%CI: 3.91 - 30.74), followed by stable or fluctuating group (HR = 5.79, 95%CI: 2.45 - 13.69), and descending group (HR = 3.84, 95%CI: 0.92 - 16.01) which had the lowest HR.
Conclusion: Individuals with stable, fluctuating or ascending VCA-IgA level showed higher risk and earlier onset of NPC was found in ascending group.