Immunoblot analysis of humoral immune response to Helicobacter pylori in children with and without duodenal ulcer

Several studies have demonstrated that enzyme-linked immunosorbent assay is not a sensitive and specific method to diagnose Helicobacter pylori infect ion in children, especially in the younger ones. Since serum immune respons e can also be determined by immunoblotting and it permits the detection of antibodies to virulence factors such as CagA and VacA, we evaluated the acc uracy of a commercial immunoblotting test to diagnose H. pylori infection a nd to assess the humoral immune response to different H. pylori antigens in 122 children who underwent upper gastrointestinal endoscopy, The presence of H. pylori was determined in antral biopsy specimens by culture, preforme d urease test, and histological analysis. H. pylori was identified by micro biological and histopathological methods in 66 children (including all of t he 21 who had duodenal ulcer). Antibodies to H. pylori were detected in 63 infected children and in 8 noninfected ones. The sensitivity, specificity, and positive and negative predictive values of the immunoblotting test were 95.5, 85.7, 88.7, and 94.1%, respectively. The number of immunoreactive ba nds increased with age (P = 0.003), and the bands of 35 kDa (P = 0.013); 89 kDa, the VacA antigen (P = 0.001); and 116 kDa, the CagA antigen (P = 0.00 004) were more frequently observed in older children. The frequency of the bands of 89 kDa (P = 0.001) and 116 kDa (P = 0.03) was higher in children w ith duodenal ulcer than in H. pylori-positive children without the disease. In conclusion, the immunoblotting test appears to be useful for the diagno sis of H, pylori infection in children, even in the younger ones.