Background
The 13C-urea breath test is currently the best noninvasive method for detecting Helicobacter pylori infection. Serological methods are less appropriate, especially for monitoring efficacy of treatment, because antibodies are present for months after the bacteria has been eradicated.
Question
What is the clinical validity of a newly developed immunoassay for detecting H. pylori antigens in fecal specimens?
Design
This prospective study compared the results of the new antigen test for H. pylori in feces with results of the 13C-urea breath test for detecting infection and monitoring treatment efficacy. Ninety subjects with dyspepsia (46 men and 44 women, age range 18-82) were screened with both tests. In addition, 115 participants (62 men and 53 women, age range 18-78) with positive breath test results were treated with triple therapy, and at least 4 weeks after treatment ended were retested with both tests.
Results
Of the 51 dyspeptic patients with positive breath test results, 47 had positive fecal antigen tests (sensitivity 92.2%, 95% confidence interval [CI] 81.1-97.8); 38 of the 39 participants with negative breath test results were also negative on the H. pylori antigen test (specificity 97.4%, 95% CI 86.5-99.9). Of the 115 H. pylori positive patients treated with triple therapy, 92 subsequently had negative breath test results; there were 5 false-positive and 2 false-negative antigen tests, resulting in a sensitivity of 91.3% and specificity of 94.6%. The results for the 205 participants showed that the overall sensitivity and specificity of the antigen fecal test with reference to the breath tests were 91.9% and 95.4% respectively.
Commentary
These results suggest that the new immunoassay has good sensitivity and specificity when compared with the urea breath test, although it was not clear how the 2 false-negative immunoassay tests were detected among the patients with negative breath test results. The recognized gold standard for the detection of H. pylori is histology from endoscopic biopsy, and the sensitivity (97.9%) and specificity (98.0%) of the urea breath test is very good when compared with histology.1 Given the ease of use and the validity of the urea breath test, as well as patient reluctance to collect fecal samples, the utility of this fecal test is not apparent, although it does appear to offer economic benefits. The authors report the new test is cheaper than the urea breath test, but its cost-effectiveness was not evaluated.
Clinical Implications
Compliance and cost-effectiveness need to be studied before the clinical utility of this new test can be determined.
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