EVALUATION OF AN IMMUNOFLUORESCENCE ASSAY FOR SPECIFIC DETECTION OF IMMUNOGLOBULIN-G ANTIBODIES DIRECTED AGAINST HELICOBACTER-PYLORI, AND ANTIGENIC CROSS-REACTIVITY BETWEEN HELICOBACTER-PYLORI AND CAMPYLOBACTER-JEJUNI

An immunofluorescence assay (IFA) for the detection of immunoglobulin G antibodies directed against Helicobacter pylori was evaluated by comparing 20 serum specimens from patients with a positive urease test on biopsy material and 20 serum specimens from patients with a negative test and with defined clinical symptoms. The resulting anti-H. pylori titers were classified as follows: negative, less-than-or-equal-to 64; borderline, 128; and positive, less-than-or-equal-to 256. By using these criteria, the IFA was subsequently tested, using 100 serum specimens from patients with gastric complaints. Overall, the titers were 71% positive, 10% borderline, and 19% negative. Depending on the patients' biopsy urease test results, the sensitivity and specificity of the assay were calculated to be 96%. Furthermore, these sera were classified into three subgroups on the basis of clinical manifestations: gastritis with 74% positive and 10% borderline titers, duodenal ulcer with 84% positive and 4% borderline titers, and gastric ulcer with 52% positive and 16% borderline titers. A serologic follow-up study was carried out with three patients with gastric ulcers who had been treated with colloidal bismuth subcitrate for 4 weeks and erythromycin for the final 2 weeks. The results indicate that a significant decrease in titer could be expected within 9 to 12 months after successful therapy, as determined by repeated negative CLO tests. Absorption experiments demonstrated that possible cross-reactivity between H. pylori and C. jejuni did not influence serodiagnosis.