Ten years after the first seroprevalence study performed in Flanders, the aim of this cross sectional study was to follow the evolution of hepatitis A, B and C prevalence. The prevalence of hepatitis A antibodies, hepatitis B surface antigen and hepatitis C antibodies was measured in oral fluid samples collected by postal survey. Using the National Population Register, an incremental sampling plan was developed to obtain a representative sampling of the general population. A total of 24,000 persons were selected and 6,000 persons among them contacted in a first wave. With 1834 participants a response rate of 30.6% was achieved. The prevalence was weighted for age and was 20.2% (95% CI 19.43-21.08) for hepatitis A, 0.66% (95% CI 0.51-0.84) for hepatitis B surface antigen and 0.12% (95% CI 0.09-0.39) for hepatitis C. The prevalence of hepatitis A and C in the Flemish population is lower in 2003 compared with the results of the study performed in 1993. The difference may be due to a real decrease of the diseases but also to differences in the methodology. The prevalence of hepatitis B surface antigen remains stable. Considering the 30% response rate and the high quality of the self-collected samples as reflect of a good participation of the general population, saliva test for prevalence study is a good epidemiological monitoring tool.

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Currently viral antigens and antibodies are detected by traditional serological tests. However, the introduction of oral fluid as an alternative medium would allow other alternatives. The collection of oral fluid is, in comparison with venepuncture, less invasive, less painful, less expensive (i.e., no trained personal required), and safe (prevention of needle stick injuries). Also large numbers of samples can be collected easily for epidemiological purposes. Forty-three HBsAg positive and seventy-three HBsAg negative paired serum/oral fluid samples were tested. They were collected from patients attending university hospitals. The oral fluid samples were collected using the Oracol collection device and they were subjected to an IgG quantification assay to ensure their quality and quantity. The detection of HBsAg in oral fluid was carried out using a modified ETI-MAK-4 ELISA. The validation of this oral fluid test gave a sensitivity and specificity of 90.7% and 100%, respectively. The modified ETI-MAK-4 ELISA is a suitable test for oral fluid samples collected by the Oracol collection device for epidemiological purposes.