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Helicobacter pylori anti-CagA antibodies: RESULTS Part 1

Symptomatic subjects
Biopsies were taken, and the presence of H pylori was determined through CLO, culture and histology. Patients were considered to be infected if one test was positive. Fifty-seven of 66 patients were found, by either one of the biopsy-based tests, to be infected with H pylori. Results of the ELISA test were compared with those of the biopsy-based tests. ELISA was shown to have 89% sensitivity (95% CI 81.5 to 95.5%), 100% specificity, 100% positive predictive value and 67% negative predictive value (95% CI 55.5 to 78.3%). Among the 66 symptomatic subjects included in the study, 32 of 38 (84%) men and 22 of 28 (79%) women were found to be H pylori-positive by ELISA – a total of 54 of 66 (82%) subjects.

Immunoblot assay was performed on 30 randomly selected ELISA-positive sera from symptomatic subjects. Table 1 shows the correlation between the prevalence of CagA antibodies and age. Twelve of 14 (86%) patients older than 45 years of age and 12 of 16 (75%) patients younger than 45 years of age were positive for CagA antibodies. Statistical analysis showed no significant difference between these age groups. CagA antibodies were detected in patients with the following histological findings: 11 of 14 (79%) with chronic gastritis, 12 of 13 (92%) with duodenal ulcer and three of three (100%) with gastric cancer (one patient also had gastric ulcer) (Table 2). VacA antibodies were detected in eight of 14 (57%) subjects with chronic gastritis, 11 of 13 (85%) with duodenal ulcer and two of three (67%) with gastric cancer. Antibodies to the other four antigens varied also in their frequency pattern (Table 2). The CIM appeared in 25 of 30 (83%) positive strips.

TABLE 1
Correlation between the presence of Helicobacter pylori anti-CagA antibodies, detected by immunoblotting, and age in symptomatic subjects who were found to be Hpylori-positive by biopsy-based tests

Age (years) CagA+ subjects, n (%)
>45 (n=14) 12 (86)
<45 (n=16) 12 (75)
Total (n=30) 24 (80)

P>0.05

TABLE 2
Prevalence of antibodies to Helicobacter pylori antigens in immunoblots of symptomatic subjects with peptic ulcer diseases

Molecular weight of antigens (kDa)
Subject group 116 (CagA) 89 (VacA) 37 35 30 19.5
Gastritis, n=14 (%) 11 (79) 8 (57) 9 (64) 9 (64) 11 (79) 7 (50)
Duodenal ulcer, n=13 (%) 12 (92) 11 (85) 10 (77) 8 (62) 13 (100) 10 (77)
Gastric cancer, n=3 (%) 3 (100) 2 (67) 2 (67) 2 (67) 3 (100) 2 (67)

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