Serodiagnosis and seroprevalence of Helicobacter pylori infection in Vietnam

University dissertation from Stockholm : Karolinska Institutet, Microbiology and Tumor Biology Center (MTC)

Abstract: Aims: The aims of the study were to establish and evaluate the best eradication treatment, the optimal diagnostic methods and the impact of Helicobacter pylori infection in Vietnam. Materials: In a treatment trial of patients with peptic ulcer disease (PUD), gastric biopsies and serum samples were obtained from 296 PUD patients (age 18-88 years). H. pylori status was confirmed by culture and/or serology at inclusion, after treatment and after 12 (+/-2) months of follow-up. Serum samples from 91 Swedish patients with gastric ulcer and 158 with duodenal ulcer, H. pylori positives by culture, and 128 asymptomatic Swedish individuals with urea breath test-confirmed H. pylori infection were included. Vietnamese population control sera were obtained from 971 individuals (age 1-88 years) in urban Hanoi and rural Ha Tay. Of these samples, 432 adults (18-88 years) from Hanoi were included in the serological evaluations and all 1971 individuals in the seroep idem io logical study. Methods The methods used were all in-house ELISA with sonicated Swedish and Vietnamese strains as antigens to measure IgG antibodies after absorption with sonicated Campylobacter jejuni to remove cross-reacting antibodies. The commercial serologic kits investigated were Pyloriset EIA-GIII (Orion Diagnostica, Espoo, Finland), HM-CAP (Enteric Products, Westbury, NY, USA) and HelicoBlot 2.1 (Genelabs, Singapore). Culture of H. pylori was performed by standard methods. The RAPD and the PCR-RFLP used a flaA gene fragment. Results: The standard, twice-daily antibiotics therapy achieved a per protocol H. pylori eradication of 87%, compared to 72% in the once-daily therapy group (p=0.03) and 39% in the antibiotics only group (p<0.01). Overall reinfection with H. pylori one year after successful eradication was 23.5%. In spite of this high rate, eradication treatment was found to be of value for PUD patients also in a developing country. The in-house ELISA showed a significantly better performance if based oil local strains. Unexpectedly, it was also found that H. pylori positive PUD patients had significantly higher antibody levels than asymptomatic, H-pylori positive population controls. Lower antibody concentrations in Asian than in European populations to H. pylori strains used in commercial kits were found to be the cause of less optimal performance of some kits. By evaluation in the target populations, however, adequately performing kits could be identified. By a validated in-house ELISA, a 74.6% overall seroprevalence of H. pylori infection in Vietnam was found. The prevalence of 78.8% in urban Hanoi was significantly higher than the 69.2% in rural Ha Tay (p = 0.0007, chi-square test). Conclusions: Standard twice-daily triple therapy with PPI is highly effective in eradicating H. pylori in Vietnamese peptic ulcer patients, despite a high reinfection rate. In-house and commercial serological kits for H. pylori need to be evaluated in the target population and appropriate adjustments need to be done. The overall seroprevalence of H. pylori infection in Vietnam is high and tile infection prevalence is higher in the urban than in the rural population.

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