Validity of a Helicobacter pylori stool antigen assay for the assessment of H-pylori status following eradication therapy

Background A Helicobacter pylori stool antigen (HpSA) test has been proposed as a valid alternative to the C-13-urea breath test (C-13-U BT) for the non-invasive detection of H. pylori infection in primary diagnosis. Published reports show conflicting results with regard to the test's diagnostic accuracy after eradication therapy. The aim of the present study was to assess the diagnostic value of the HpSA test and to determine the optimal discriminating cut-off value in patients following H. pylori eradication therapy. Method Stool samples were collected and the C-13-UBT was performed in 113 patients 4-6 weeks after eradication therapy, A validated test protocol for the C-13-UBT was used. Stool specimens were analysed with the Premier Platinum HpSA enzyme immunoassay (EIA), A receiver operator characteristics (ROC) analysis was performed to define the optimal cut-off value on the basis of the results of the C-13-UBT. Results The results of the C-13-UBT showed that H. pylori eradication was successful in 83/113 (73%) patients. According to the manufacturer, the cut-off value for the HpSA test is 0.14 optical density, but this does not appear to be valid after eradication therapy (sensitivity 76.7%, specificity 98.8%). On the basis of ROC analysis, the optimal cut-off value after therapy was determined to be 0.11 optical density, giving a sensitivity of 93.3% and a specificity of 93.9%. Conclusion The HpSA test is a valid test for the assessment of H. pylori status after eradication therapy, provided an adjusted cut-off value is applied. Eur J Gastroenterol Hepatol 13:673-676 (C) 2001 Lippincott Williams & Wilkins.