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Effects of stool dilution on the faecal Helicobacter pylori antigen test
1Department of Pediatrics, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. tsimizut@aol.com
Insights
Diluting stool samples for the faecal Helicobacter pylori antigen test generally yields accurate results up to a 1:10 dilution. Higher dilutions, like 1:50, may lead to false negatives, even with low antigen levels.
Area of Science:
- Gastroenterology
- Microbiology
- Diagnostic Testing
Background:
- Helicobacter pylori infection is a significant cause of gastrointestinal diseases.
- Accurate detection of H. pylori is crucial for effective treatment.
- The faecal antigen test is a common diagnostic method, but its performance can be affected by sample preparation.
Purpose of the Study:
- To evaluate the impact of stool sample dilution on the sensitivity and specificity of the faecal H. pylori antigen test.
- To determine the optimal dilution threshold for reliable H. pylori antigen detection in stool.
Main Methods:
- Stool samples from nine H. pylori-infected children were analyzed.
- Samples were serially diluted with normal saline (1:1, 1:5, 1:10, 1:50, 1:100, 1:500).
- Optical density (OD) was measured to quantify antigen levels and assess test results at each dilution.
Main Results:
- The faecal H. pylori antigen test remained positive for all samples diluted 1:10 or less.
- One sample with initially low OD values transitioned from positive to negative at a 1:50 dilution.
- This indicates a potential for false-negative results at higher dilutions.
Conclusions:
- Stool dilutions of 1:10 or less are generally reliable for the faecal H. pylori antigen test.
- Higher dilutions (e.g., 1:50) may increase the risk of false-negative results, particularly in cases with low initial antigen levels.
- Careful consideration of sample dilution is recommended for accurate H. pylori diagnosis.
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.