Real-time monitoring of Helicobacter pylori eradication therapy by testing stool antigen

Evaluation of Helicobacter pylori stool antigen test before and after eradication therapy

BACKGROUND AND AIM

The Helicobacter pylori stool antigen (HpSA) test is useful for initial diagnosis of H. pylori infection, but there is disagreement regarding its diagnostic accuracy after eradication therapy. The aim of the present study was to evaluate the diagnostic accuracy of the HpSA test before and after eradication therapy.

METHODS

One hundred and thirty-six patients underwent upper gastrointestinal endoscopy with biopsies for the diagnosis of H. pylori infection using culture, histology and the rapid urease test. Fifty-four H. pylori-positive patients were treated with 1-week triple therapy. Six to 10 weeks after the end of therapy, the patients underwent re-endoscopy and received the same biopsy-based methods. In addition, the 13C-urea breath test was performed. The HpSA test was performed before and 6-10 weeks after the end of therapy. In 23 patients, the HpSA test was also performed at the end of therapy.

RESULTS

Before therapy, the sensitivity and specificity of the HpSA test was 98.3% (95% confidence interval (CI): 95.9-100%) and 95.0% (95% CI: 75.1-99.9%), respectively. At the end of therapy, the HpSA tests were all negative both for eradication and non-eradication patients. The sensitivity and specificity of the HpSA test after eradication therapy were 90% (95% CI: 55.5-99.7%) and 97.7% (95% CI: 93.3-100%), respectively.

CONCLUSIONS

The HpSA test is a useful method for the diagnosis of H. pylori infection before and after eradication therapy.

Effects of stool dilution on the faecal Helicobacter pylori antigen test

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.

Helicobacter pylori antigens in stool specimens of gastritis children before and after treatment

BACKGROUND

Various testing methods are successfully applied to the diagnosis of Helicobacter pylori infection, but noninvasive techniques are still needed for therapeutic monitoring, especially in children. In the search for new noninvasive techniques for the diagnosis of H. pylori infection, the authors evaluated an enzyme immunoassay for the detection of H. pylori antigen in stool (HpSA).

METHODS

The authors studied 62 H. pylori-positive children with chronic gastritis and 45 control subjects. H. pylori infection was diagnosed using cultures and histology of gastric biopsy specimens and a stool antigen test before treatment (clarithromycin, amoxicillin, omeprazole for 7 days) and 4 weeks to 6 weeks after treatment.

RESULTS

Before therapy, antigen in stool was detected in 55 of 62 H. pylori-positive patients, which indicates that the sensitivity of the HpSA test was 88.7%. Of the 45 control subjects (with negative culture and histology results), 43 had negative results for H. pylori in the stool test (specificity, 95.5%). After completion of therapy, eradication was obtained (and confirmed by culture and histology) in 53 of the 62 H. pylori-positive children (85.5%). Four weeks to 6 weeks after eradication therapy, the sensitivity, specificity, positive predictive value, and negative predictive value of the stool antigen (HpSA) test were 88.9%, 96.2%, 80%, and 98%, respectively.

CONCLUSIONS

The accuracy of the HpSA test for the detection of H. pylori in human stool 4 weeks to 6 weeks after treatment is comparable with the accuracy of the culture results. The stool antigen (HpSA) test was found to be a useful method for posttreatment eradication testing of infection in children.