Seroconversion and seroreversion in IgG antibodies to Helicobacter pylori:: a serology based prospective cohort study

Study objectives-To assess the incidence of seroconversion and seroreversion in IgG antibodies to Helicobacter pylori within a 11 year observation period using these events as markers for acquisition and loss of the infection, respectively. Design-Population based prospective cohort study Setting-Northern part of Copenhagen County, Denmark Participants and methods-A random sample of 2527 Danish adults were examined and blood obtained in 1983 and in 1994. Matching pairs of sera were analysed for the presence of IgG and IgM antibodies to H pylori with an in house enzyme linked immunosorbent assay. Participants who were seronegative at study entry and seropositive at follow up and had a fourfold increase in baseline IgG antibody levels were categorised as seroconverters and regarded as having acquired H pylori infection. Participants who were seropositive at study entry and had at least a fourfold decrease in baseline IgG antibody revels at follow up were assumed to have lost the infection (seroreverters). Results-The seroprevalence of H pylori infection was 24.7 (95% confidence intervals (95% CT) 23.0, 26.4)% in 1983 and 24.5 (95% CI 22.8, 26.2) % in 1994. A total of 14 participants seroconverted within the observation period (cumulative 11 year incidence proportion: 1.0 (95% CI 0.5, 1.5) %). Having increased IgM antibody levels at study entry significantly increased the likelihood of IgG seroconversion (relative risk 6.4 (95% CI 2.1, 19.6). Seroreversion was seen in 48 participants (cumulative 11 year incidence proportion: 7.7 (95% CI 5.6, 9.8) %). Conclusions-Changes in H pylori infection status with time are rare in Danish adults. Few adults become infected with H pylori in Denmark.