Effect of cagA status on the sensitivity of enzyme immunoassay in diagnosing Helicobacter pylori-infected children

Background. The aims of our study were twofold. First, we sought to evaluate in symptomatic children the influence of the Helicobacter pylori genotype on gastritis, abdominal pain, and circulating anti– H. pylori IgG antibodies (anti– H. pylori IgG) or pepsinogen A (PGA) and C (PGC). Additionally, we sought to assess anti– H. pylori IgG, PGA, and PGC patterns in a large cohort (N = 921) of asymptomatic children.
Materials and Methods. In 183 symptomatic children, H. pylori infection and the presence of gastritis were evaluated by histology. In a subgroup of 20 H. pylori –positive children, the H. pylori genotype was evaluated also by polymerase chain reaction. Nine hundred and twenty-one asymptomatic children, aged 11 to 14 years, were studied by anti– H. pylori IgG, PGA, and PGC serum determination.
Results. The infection was found in 33 of 183 symptomatic children; among the 20 H. pylori –positive children for which the H. pylori genotype was available, cag A was present or absent in equal percentages. H. pylori infection was associated with more severe gastritis and higher serum levels of anti– H. pylori IgG and PGC but not with abdominal pain. In infected children, higher levels of anti– H. pylori IgG and the presence of abdominal pain were associated with infections caused by cag A-positive strains. In the cohort of 921 asymptomatic children, raised levels of anti– H. pylori IgG, PGA, and PGC were found in approximately 5% of the cases.
Conclusions. Infection with cag A-positive H. pylori strains can be associated with increased frequency of reported abdominal pain and higher circulating levels of anti– H. pylori IgG. The serological assessment of H. pylori IgG using H. pylori antigens containing significant amounts of cagA protein may, therefore, underestimate the true prevalence of infection.