Effects of stool dilution on the faecal Helicobacter pylori antigen test

Abstract

Objective: To examine the effects of stool dilution on the results of the faecal Helicobacter pylori antigen test. Methods: Stool samples from nine children with H. pylori infection were diluted with normal saline at dilutions of 1, 5, 10, 50, 100 and 500 times, and optical density (OD) was measured. Results: The faecal H. pylori antigen test yielded positive results for all samples at dilutions of 1:10 and less, although the sample from the case whose original stool showed the lowest OD value changed from positive to negative at a dilution of 1:50. Conclusion: Our results suggest that stools at dilutions of less than 1:10 usually do not yield false-negative results in the faecal H. pylori antigen test, even in patients with low faecal antigen levels.