Prevalence and Significance of Anti-HDV Antibodies in HBsAg-Negative Subjects

Objective: The presence of anti-HDV antibodies in HBsAg-positive subjects suggests HBV/HDV co-infection. Anti-HDV antibodies may remain after recovery and the disappearance of HBsAg, but active HDV and/or HCV infections can also sometimes decrease HBsAg production. However, there are few epidemiological data concerning anti-HDV antibodies in HBsAg-negative subjects. The aims of this study were to determine the prevalence of anti- HDV antibodies in HBsAg-negative subjects with other markers of HBV infection in an urban area of northern Italy in order to evaluate their significance in the presence/absence of HCV, and to contribute to HDV epidemiology by comparing the results with those obtained in a previous study of HBsAg-positive subjects in the same area.

Methods: Anti-HDV antibodies were retrospectively investigated in 1287 HBsAg-negative/anti-HBc-positive subjects who hade been examined for HBV markers. Signs of possible liver alterations and HCV and HIV infections were sought in the clinical records of the anti-HDV-positive patients, and HBV-DNA, anti-HBc IgM, anti-HDV IgM and HDV-RNA were detected.

Results: Thirteen samples (1.0%) were anti-HDV-positive. The clinical evaluation of 12 of these patients showed that nine had had previous HBV/HDV co-infections; two had concomitant HCV infection, and one occult HBV infection. The prevalence of past HDV infection was 0.7%. The prevalence of anti-HDV in HBsAgpositive patients in the same area was 4.9%.

Conclusion: The prevalence of past HDV infection in the study area is low, but interference from HCV is possible in a few cases. Comparison with data obtained from HBsAg-positive subjects suggests that about one-quarter of HBV/HDV co-infections resolve naturally.