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 (13)C 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 40 minutes after ingestion of 100 mg (13)C labelled urea. (13)C 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, >/=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.