Introduction H pylori has a prevalence of around 40%–50% in the UK.¹ Rapid urease test (CLO test) is commonly used in the endoscopy units around the UK to detect H pylori. False negative CLO test results are associated with early reading of the test and use of acid suppressing medication.² We assessed the reliability of CLO test and prevalence of false negative results.

Methods Retrospective data analysis was performed by auditing case notes of 85 patients with positive histology for H pylori. CLO test was performed by using Kimberly-Clarke CLO test kit and the reading time was between 12 and 24 h.

Results Male:Female ratio was 43:42. False negative CLO test was found in 37 patients (43.6%), out of which 21 (56.7%) were not taking PPI or stopped PPI for at least 2 weeks prior to the endoscopy. 16 (43.2%) patients in the false negative group were drinking alcohol regularly as compared to 11 (22.9%) in CLO positive group, while 28 (58.3%) in CLO positive group were non drinkers. Regular drinkers taking PPI before the test had a low percentage (3/12; 25%) of CLO positive results while non-drinkers not on PPI show a high percentage (28/36; 77.8%) for positive results [p=0.013]. Also, in patients who had false negative CLO test, approximately 45% of patients consume regular alcohol. Absence of gastritis was associated with a slightly higher rate of false negative CLO test result (27.1% vs 20.8% for CLO positive) [p=NS]. Use of PPI only showed to contribute to false negative CLO test in absence of gastritis endoscopically (70% in patients with no gastritis and taking PPI) [p=NS]. Smoking was not associated with false negative CLO test.

Conclusion High incidence of false negative CLO test result in our study suggests that CLO alone might not be a reliable test even in patients not taking acid suppressing medication. Regular alcohol use may contribute to false negative CLO test results. Gastric histology is better than CLO test in patients who are regular alcohol drinkers and taking PPI but in whom OGD does not show gastritis. Further studies need to be done to consider role of targeted gastric biopsies to increase the yield of CLO test.

Competing interests None declared.

References 1. Fuccio L, Laterza L, Zagari RM, et al. Treatment of H. pylori infection. BMJ 2008;15;337.

2. Prince MI, et al. The CLO test in the UK, inappropriate reading and missed results. Eur J Gastroenterol Hepatol 1999.