Accuracy of an enzyme immunoassay for the detection of Helicobacter pylori in stool specimens in the diagnosis of infection and posttreatment check-up

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Abstract
The aim of this study was to assess the reliability of a newly developed enzyme immunoassay for Helicobacter pylori-specific antigen detection in stools (HpSA) compared to other standardized diagnostic techniques such as histology (H), rapid urease test (RUT) and 13C-urea breath test (UBT) to diagnose H. pylori infection and to evaluate its usefulness in determining H. pylori status after treatment. One hundred eighty-eight patients referred to our department for upper gastrointestinal endoscopy were included. H. pylori infection was confirmed in all patients by HpSA test in stools, RUT, UBT, and H. Patients were defined as positive for H. pylori if RUT and UBT or H were positive. A total of 142 symptomatic patients received eradication treatment and were reassessed 6 wk after therapy; for 70 of these patients, stool samples were also collected at 24 h and 6 months after finishing eradication treatment. In the posttreatment follow-up, UBT was used as gold standard. The sensitivity of HpSA test for the diagnosis of H. pylori infection using a cut-off value of 0.130 was 89.5% and its specificity 77.8%. This specificity was lower than that obtained with UBT, H, and RUT. In the early follow-up the sensitivity of HpSA test was null. At 6 weeks and at 6 months post-treatment its sensitivity was 70.4% and 50% and its specificity was 81.6% and 79.3%, respectively. The HpSA stool test, using a cut-off value of 0.130, may be useful for the primary diagnosis of H. pylori infection, with sensitivity similar to that obtained with other standard tests, but with less specificity. HpSA test is not useful for early monitoring of treatment efficacy. At 6 wk and at 6 months posttreatment, HpSA test lacks accuracy as compared to UBT for evaluating the outcome of the eradication treatment.