Helicobacter pylori is the cause of type B gastritis and associated with peptic ulcer disease. Various methods are available for detecting H pylori, but all have limitations.1 H pylori infection can be diagnosed by tests requiring endoscopy (rapid urease test, histology, culture) and by non-invasive tests (carbon-13 urea breath test, serology, stool tests). The urea breath test is currently the most important test for follow up after H pylori treatment.1 Serology is widely used for screening patients for H pylori infection; it has a good sensitivity, is fast, and relatively inexpensive.1 However, the urea breath test is expensive and requires specialised equipment, and serological tests cannot be used after H pylori treatment and may have a lower specificity.
Most patients infected with H pylori are treated by general practitioners, who need an easy test for it. Recently, an immunoassay has been developed that can detect H pylori antigen in human faeces,2 but it has not been validated for clinical use. We studied patients undergoing routine endoscopy to determine sensitivity and specificity of this immunoassay in comparison with standard methods.
Subjects, methods, and results
We recruited 102 consecutive patients (58 men, 44 women) undergoing upper endoscopy. Our study was approved by the local ethics committee. We determined H pylori status in all patients by rapid urease test, histology, and culture using standard methods.1 Patients were considered positive if at least two of the three tests were positive. Patients were asked to collect a specimen from their first stool after endoscopy and to post it to us. We analysed the stool specimens for H pylori antigen using the Premier Platinum HpSA Immunoassay as described by the manufacturer (Meridian Diagnostics, Cincinnati, OH, USA). The test is based on a capture of polyclonal antibodies to H pylori adsorbed to microwells. The results were analysed by spectrophotometric determination and considered positive if the optical density was >0.12 and negative if it was <0.10. We calculated the test's sensitivity, specificity, and positive and negative predictive values.
Forty nine of the patients had dyspepsia, 33 had active ulcer disease, 16 had gastric or duodenal erosions, and four had gastric polyps. The table shows the results of the immunoassay compared with the standard tests: two stool tests were classified as false negative and four as false positive. The immunoassay thus had a sensitivity of 96% (95% confidence interval 90.6% to 100%), specificity of 93% (85.1% to 99.5%), positive predictive value of 92%, and negative predictive value of 96%.3
Comment
Our study indicates that this immunoassay could be used as a routine diagnostic tool for H pylori infection. It seems to overcome some limitations of previous tests. We found a high sensitivity and specificity compared with reference tests. This new immunoassay has the advantage of being non-invasive, easy and fast to perform, and cheaper than the urea breath test. The bacterium does not need to be alive; preliminary data suggest that the test can be used even during H pylori treatment.4
The new immunoassay seems to meet the requirements of general practitioners, who treat most patients infected with H pylori, because it is easy to perform, requires no blood samples to be taken, and its costs are similar to those of serological tests. Other stool tests have been developed,5 but they cannot be used for clinical practice, either because they require specialised equipment (culture, polymerase chain reaction, etc) or because they have not been validated for clinical use (immunoassay).
This stool immunoassay represents a new, accurate, and non-invasive method for H pylori infection that overcomes the limitations of existing tests.
Table.
Detection of H pylori infection by stool immunoassay in comparison with standard tests (histology, rapid urease test, and bacteriology). Values are numbers of tests
| Standard tests | ||
|---|---|---|
| H pylori positive (n=50) | H pylori negative (n=52) | |
| Stool immunoassay: | ||
| Positive | 48 | 4 |
| Negative | 2 | 48 |
Footnotes
Competing interests: None declared.
References
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