Stool antigen assay (HpSA) is less reliable than urea breath test for post-treatment diagnosis of Helicobacter pylori infection

Background: The diagnostic yield of the stool antigen test (HpSA) in evaluating the results of Helicobacter pylori eradication therapy is controversial, but many studies have used only the C-13-urea breath test (C-13-UBT) as a gold standard which has greatly reduced their relevance. Aim: To compare the reliability of HpSA and C-13-UBT in patients post-treatment using biopsy-based methods as reference tests. Methods: A total of 100 consecutive dyspeptic patients (42 male and 58 female; mean age, 56 +/- 18 years) were enrolled in our study. All patients were H. pylori positive on the basis of at least two biopsy-based methods, and underwent 1 week of treatment with various triple therapies. They were again endoscoped 4 weeks after completing therapy and six biopsyspecimens were taken from the gastric antrum and corpus for rapid urease test, histology and culture. HpSA and C-13-UBT were also performed within 3 days of the second endoscopy. Results: On the basis of biopsy-based tests, infection was eradicated in 77 patients but continued in 23. Three false negatives were observed with HpSA and two with C-13-UBT. In contrast, the number of false positives was significantly higher (P < 0.01) with HpSA than with C-13-UBT (nine vs. one), confirming the lower specificity of the former test. The overall accuracy of HpSA was 88% vs. 97% for C-13-UBT (P < 0.02). Conclusions: HpSA has lower diagnostic value than C-13-UBT in the evaluation of the outcome of anti-H. pylori therapy. C-13-UBT remains the first-line diagnostic method to monitor eradication results. The use of HpSA should be reserved for those settings in which C-13-UBT is not available.