Evaluation of the effect of presence of blood in the stomach on endoscopic diagnostic tests for Helicobacter pylori infection.

ABSTRACT

Introduction: Presence of blood in the stomach has been thought to affect the performance of diagnostic tests used in detecting Helicobacter pylori (H. pylori) in the stomach. This study evaluated the effect of blood on the efficacy of rapid urease test (RUT) and microscopic appearance of the biopsy after staining with Giemsa stain. Materials and Methods: Patients with bleeding oesophageal varices who met the inclusion criteria were tested for H. pylori by RUT and microscopic examination of the biopsy. A repeat endoscopy, RUT and histology were done one month following initial presentation. The performance of the diagnostic tests was evaluated with and without the presence of intraluminal blood. A combined result of the two tests, RUT and histology, carried out in presence or absence of blood for the diagnosis of H. pylori, when considered together was considered as the gold standard. Results: Thirty six patients included in the study were in the ages ranging between 15-60 years (mean age = 44.14 years ±2.1). The combination of tests at both visits showed 20/36 (55.6%) patients were positive for H. pylori. The decrease in H. pylori positivity in the presence of blood was significant for RUT (8.3% vs. 38.9%; P=0.005) and combined test (19.4% vs. 47.2%; P=0.02) but the decrease in positivity for histology (11.1% vs 30.6%) was not significant (P=0.08). In the presence of blood, the sensitivity of RUT, histology and combined tests were 15%, 20% and 35%, respectively. In the absence of blood, the sensitivity of RUT, histology and combination of tests was 70%, 55% and 85%, respectively. Conclusion: Blood in the stomach significantly decreased the sensitivity of RUT, histology and the combination of both. Negative results of these tests in acute upper gastro intestinal (GI) bleeding should therefore be interpreted carefully.