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 (e ndoscopy) or indirect (urea breath test, serology). Aims-To evaluate a new enzyme immunoassay (EIA) which detects H pylori anti gens in faeces, by comparing its sensitivity and specificity in children wi th the C-13 urea breath test (UBT). Methods-A total of 119 children underwent a UBT and provided a faecal sampl e 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 i ngestion of 100 mg C-13 labelled urea. C-13 enrichment of breath was measur ed by isotope ratio mass spectrometry. Faeces were stored at -70 degrees C until antigen testing, using the EIA. Samples were read spectrophotometrica lly at 450 nm and results were interpreted using recommended cut offs of op tical 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 result s. Sensitivity and specificity were calculated using the manufacturer's cut off compared with UBT. Results-Sensitivity and specificity were 88% and 82%, respectively. Negativ e 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 va lue suggests a role in screening out uninfected children.