Background and Goal The rapid urease CLOtest is commonly used during endoscopy to diagnose the presence of Helicobacter pylori. The aim of this study was to determine whether the sensitivity of the CLOtest can be improved by increasing the number of gastric antral biopsies from 1 to 4.

Methods The study included 100 adult patients who were referred for upper gastrointestinal endoscopy and tested positive for H. pylori infection on ¹³C urea breath test (“gold standard”). These 100 patients were then randomly divided into 4 equal groups (groups 1 to 4), and underwent an upper gastrointestinal endoscopy. Patients in group 1 had 1 gastric antral biopsy during endoscopy, whereas those in groups 2, 3, and 4 had 2, 3, and 4 biopsies, respectively. The biopsies were placed in the rapid urease CLOtests, which were incubated at room temperature for up to 24 hours, and read for positive results at 1, 6, and 24 hours.

Results About half of the patients (52%) had a positive CLOtest in group 1, compared to 68% in group 2, 76% in group 3, and 96% in group 4 (group 1 vs. 4 P<0.01). After 1 hour of incubation 96% of the patients in group 4 had a positive CLOtest, compared to 40% in group 3, 12% in group 2, and 4% in group 1.

Conclusions Increasing the number of gastric antral biopsies from 1 to 4 significantly improves the sensitivity of the CLOtest, eliminates sampling error, and hastens the time needed by the test to become positive for the diagnosis of H. pylori infection.