Seroepidemiology of Helicobacter pylori infection and hepatitis A in a rural area: evidence against a common mode of transmission

Abstract

Background and aims: Recent studies have shown that the age-specific seroprevalence of H pylori infection parallels hepatitis A (HAV), suggesting similar modes of transmission. The aim of this study was to investigate the seroepidemiology of H pylori and HAV in the same setting.

Patients: A sample of 705 resident subjects (273 men, age range 1-87 years, median 50) who attended the outpatient medical centre of the rural town of Cirò, Southern Italy (11,000 inhabitants) for blood testing were recruited.

Methods: All subjects completed a structured questionnaire. A serum sample was drawn from each subject and assayed for H pylori IgG by a validated in house enzyme linked immunosorbent assay. Antibodies to HAV were determined in 466 subjects (163 men, age range 1-87 years, median 49). A measure of agreement between H pylori and HAV seropositivity, the kappa statistic, was used.

Results: Overall, 446 (63%) subjects were seropositive for H pylori. Of the 466 subjects screened for both H pylori and HAV, 291 (62%) were seropositive for H pylori and 407 (87%) for HAV. Cross-tabulation of these data showed that 275 (59%) were seropositive and 43 (9%) seronegative for both H pylori and HAV, 16 (3%) were seropositive for H pylori, and 132 (28%) were seropositive for HAV (OR = 5.6, CI 3 to 10). There was a parallel, weakly correlated (r = 0.287) rise in the seroprevalence of the two infections with increasing age. However, the agreement between H pylori and HAV seropositivity was little better than chance (kappa = 0.21) and in those aged less than 20 years it was worse than chance (kappa = -0.064). Furthermore, multiple logistic regression analysis did not show any risk factor shared by both infections.

Conclusions: The correlation between H pylori and HAV reflects the age-specific seroprevalence of both infections rather than a true association. This study provides evidence against a common mode of transmission of H pylori and HAV.

Figure 1

: Seroprevalence of H pylori and hepatitis A virus in the 466 subjects tested for both infections by age group: 1-10 years (n = 24), five H pylori positive, four HAV positive; 11-20 years (n = 20), eight H pylori positive, six HAV positive; 21-30 years (n = 62), 24 H pylori positive, 48 HAV positive; 31-40 years (n = 57), 36 H pylori positive, 55 HAV positive; 41-50 years (n = 76), 54 H pylori positive, 73 HAV positive; 51-60 years (n = 81), 58 H pylori positive, 77 HAV positive; 61-70 years (n = 89), 63 H pylori positive, 88 HAV positive; 71-80 years (n = 43), 33 H pylori positive, 42 HAV positive; >80 years (n = 14), 10 H pylori positive, 14 HAV positive.

Figure 2

: Seropositivity for H pylori and hepatitis A virus in the 466 subjects tested for both infections. The strength of agreement is calculated by κ statistic analysis according to Landis and Koch¹⁵ and shown in (A) the overall population and (B) in the subset of 44 subjects aged between 1 and 20 years. The seroprevalence of H pylori and hepatitis A virus was 62% and 87%, and 29% and 23%, respectively, in the two groups.