effect of GASTROINTESTINAL bleeding on THE sensitivity of diagnostic tests for HELICOBACTER pylori infection

Background– Bleeding duodenal ulcer (BDU) may reduce the positive rate of urease test. This study evaluates if bleeding can affect other diagnostic tests for H. pylori.Methods– In this study, during 1997–99, 60 patients with BDU (group 1) and 60 patients with non-bleeding duodenal ulcer (NBDU) (group 2) were enrolled. All patients were endoscopied and three-biopsy specimen, urea breath test (UBT) and serologic assay for anti-H. pylori antibody (IgG) were performed. Any patient with positive anti-H. pylori antibody was considered as an infected patient. Results– There were 59 (98%) and 58 (96%) infected patients in group 1 and group 2 respectively. The positive rates for urease, biopsy and UBT in group 1 were 50 %, 75% and 95% while these rates were 90%, 90% and 96% in group 2, respectively. The patients in group 1 were divided into subgroups based on the presence (1a) or absence (1b) of blood in the antrum. The positive rate for urease, biopsy and UBT were 50% vs. 70%, 75% vs. 80%, and 95% vs. 93% in subgroup 1a and 1b, respectively. There was significant (p < 0.05) difference between BDU patients and NBDU patients in urease test results while for other tests, there were not any significant differences. Also, there was not any significant difference in subgroups 1a and 1b in their test results for H. pylori.Conclusion– BDU significantly reduces true positive rate of urease test while its effect on positive rate of other tests in negligible. We recommend using other diagnostic tests for H. pylori infection in the case of BDU rather than urease test.