Effects of stool dilution on the faecal Helicobacter pylori antigen test

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.