Comparison of an enzyme immunoassay for the detection of Helicobacter pylori antigens in the faeces with the urea breath test

Abstract

Background - Current diagnostic tests for Helicobacter pylori are invasive (endoscopy) or indirect (urea breath test, serology). Aims' - To evaluate a new enzyme immunoassay (EIA) which detects H pylori antigens in faeces, by comparing its sensitivity and specificity in children with the 13C urea breath test (UBT). Method - A total of 119 children underwent a UBT and provided a faecal sample for antigen testing within seven days. After an overnight fast each child provided a pretest breath sample, and samples at 30 and 40 minutes after ingestion of 100 mg 13C labeled urea. 13C enrichment of breath was measured by isotope ratio mass spectrometry. Faeces were stored at -70°C until antigen testing, using the EIA. Samples were read spectrophotometrically at 450 nm and resets were interpreted using recommended cut offs of optical density <0.14 as negative, ≥0.16 as positive, with ≥0.14 and <0.16 representing equivocal results. Sensitivity and specificity were calculated using the manufacturer's cut off compared with UBT. Results - Sensitivity and specificity were 88% and 82%, respectively. Negative and positive predictive values were 97% and 58%. Conclusions - The EIA is an alternative, non-invasive, and easy to use method for the detection of H pylori in children. Its high negative predictive value suggests a role in screening out uninfected children.