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

Study objectives-To assess the incidence of seroconversion and seroreversio n in IgG antibodies to Helicobacter pylori within a 11 year observation per iod 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 examine d and blood obtained in 1983 and in 1994. Matching pairs of sera were analy sed for the presence of IgG and IgM antibodies to H pylori with an in house enzyme linked immunosorbent assay. Participants who were seronegative at s tudy entry and seropositive at follow up and had a fourfold increase in bas eline IgG antibody levels were categorised as seroconverters and regarded a s 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 i ntervals (95% CT) 23.0, 26.4)% in 1983 and 24.5 (95% CI 22.8, 26.2) % in 19 94. 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 li kelihood of IgG seroconversion (relative risk 6.4 (95% CI 2.1, 19.6). Seror eversion was seen in 48 participants (cumulative 11 year incidence proporti on: 7.7 (95% CI 5.6, 9.8) %). Conclusions-Changes in H pylori infection status with time are rare in Dani sh adults. Few adults become infected with H pylori in Denmark.