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

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 C-13 urea breath test (UBT). Methods-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 30 minutes after ingestion of 100 mg C-13 labelled urea. C-13 enrichment of breath was measured by isotope ratio mass spectrometry. Faeces were stored at -70 degrees C until antigen testing, using the EIA. Samples were read spectrophotometrically at 450 nm and results were interpreted using recommended cut offs of optical density <0.14 as negative, greater than or equal to 0.16 as positive, with greater than or equal to 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.