Post-treatment diagnostic accuracy of a new immunoassay to detect Helicobacter pylori on stools

BACKGROUND: Helicobacter pylori has attracted increasing attention among gastroenterologists because of its pathogenic potential, stimulating the search for non-invasive diagnostic tests. AIMS: In this study the efficacy of a new enzyme immunoassay designed to detect H. pylori antigens in stools (HpSA) was evaluated before and after eradication therapy. METHODS: HpSA was performed on stool samples collected from 268 patients whose H. pylori status was defined on the basis of concordant results for the (13)C-urea breath test, rapid urease test and histology. The H. pylori-positive patients were treated with a 1-week triple therapy to eradicate the infection. One (T30) and 3 months (T90) after the end of therapy, (13)C-urea breath test and HpSA were repeated in the treated patients. RESULTS: The overall diagnostic accuracy of HpSA at T30 (83%, 95% confidence interval (CI) 77--89%) was significantly lower in comparison to the values obtained at baseline (94%, 95% CI: 91--97%) and at T90 (97%, 95% CI: 94--99%). No significant difference was found between the diagnostic accuracy of HpSA at baseline and at T90 (P=0.253). CONCLUSIONS: The present data suggest that HpSA provides a low diagnostic accuracy when used shortly after treatment. It needs a longer period of follow-up (8--12 weeks) to reach a reliability comparable to the (13)C-urea breath test.