Accuracy of a new monoclonal stool antigen test in post-eradication assessment of Helicobacter pylori infection: comparison with the polyclonal stool antigen test and urea breath test.

BACKGROUND AND AIM: The enzyme immunoassay based on polyclonal antibodies (HpSA) represents a valid method for the detection of Helicobacter pylori antigens in stool specimens, but some controversial results were reported in post-eradication setting. A new monoclonal enzyme immunoassay (FemtoLab H. pylori, Connex) has been developed. The present study compares the diagnostic accuracy of the two tests after eradication therapy. PATIENTS AND METHODS: Stool samples were collected and urea breath test and endoscopy performed in 325 patients (161 F, 164 M, age 17-78 years), 4-8 weeks after standard triple eradication therapy. The FemtoLab and HpSA tests were performed in accordance with the manufacturer's protocol. H. pylori infection was confirmed if culture alone or both urease test and histology were positive and was considered absent if all three tests were negative. RESULTS: H. pylori was eradicated in 231 patients (71.1%). Urea breath test showed the best performances with sensitivity 98.9% and specificity 99.5%. The sensitivity of FemtoLab was 88.3%, specificity 94.8%, positive and negative predictive values 87.4% and 95.2%. Corresponding HpSA values were 73.4%, 97.8%, 93.2% and 90%. Sensitivity and negative predictive value of FemtoLab were significantly better than HpSA. Adjusting the cut-offs according to a ROC curve improved not significantly the sensitivity of the two tests. CONCLUSIONS: Urea breath test shows the best accuracy in the assessment of H. pylori infection. Between the stool tests, the FemtoLab due to its higher sensitivity is to prefer in the post-eradication assessment of H. pylori infection.