Usefulness of Helicobacter pylori antigens detection in stools for infection diagnosis and confirming eradication

BACKGROUND: A new immunoassay to detect H. pylori antigen in stool (HpSA) has been developed. We started this study to know the sensitivity and specificity of this test as diagnostic tool of H. pyori infection and eradication control. PATIENTS AND METHODS: Forty patients were recruited to study H. pylori infection, At endoscopy, biopsy samples were taken for culture, histology and urease test. Stool specimens were tested by HpSA and serum sample for serology. Patients were defined as H. pylori positive if histology, urease test or culture were positive. Forty-two patients treated with omeprazol based triple therapy were screened 8 weeks after treatent for eradication control using urea breath test, HpSa and serology, Patients with UBT negative were defined as eradicated. RESULTS: As diagnostic tool: 34 out of 40 patients were infected (85%). HpSA was positive in 31 out of 34 patients, and achieve 3 false negative and 1 false positive (sensitivity: 91%, specificity: 84%). IgG anti-H. pylori was positive in 31 out of 34 infected patients, with 3 false positive and 3 false negative (sensitivity 91%, specificity 50%). In eradication control (n = 42), HpSA was negative in 33/38 successfully eradicated patients, and positive in all four noneradicated patients. Five patients eradicated showed positive HpSA (specificity 87%, positive predictive value: 87%, negative predictive value: 100%). IgG serology was negative in only a third of eradicated patients. CONCLUSIONS: The stool assay was an accurate tool for diagnosis of H. pylori infection and eradication control.