Seroepidemiological Study on Trend of Helicobacter pylori Infection Rate in a small population

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We conducted a seroepidemiological study on trend of Helicobacter pylori infection rate in a small population. We collected serum samples from about 6,000 residents whose age were 30 years old or older in a small town in 1987,1988,1992,1993 and 1997 and had stored in freezers. We measured Ig-G antibody of Helicobacter pylori of the sera by EIA method. Positive Helicobacter pylori infection was judged by the Ig-G antibody level of 1+ or more. Helicobacter pylori infection rates in 1988,1992 and 1993 were lower than those in 1987 and 1997. This might be due to the poor preparation before freezing or poor condition during the freezing period. The rates in males were higher than in females in both 1987 and 1997. The age-specific rates increased with age except for those in 80 years old or more in both 1987 and 1997. Birth cohort analysis showed the same phenomenon. The age specific rates in same age groups slightly decreased from 1987 through 1997. Among 533 residents measured in both 1987 and 1997, the persistent positive rate was about 70% and the persistent negative was about 20%. The positive sero-conversion rate was about 5% and the negative was about 6%. There is only a regional hospital in the study area and physicians did not conduct the eradication therapy for patients with Helicobacter pylori infection in these 10 years. These suggest that there is a spontaneous sero-conversion of Helicobacter pylori infection among adult residents, though the proportion in population is small.