Evaluation of a novel monoclonal enzyme immunoassay for detection of Helicobacter pylori antigen in stool from children

Abstract

Background: Reliable non-invasive methods for detection of Helicobacter pylori infection are required to investigate the incidence, transmission, and clearance of infection in childhood.

Aim: To evaluate a new monoclonal enzyme immunoassay (EIA) (FemtoLab H pylori Cnx) for detection of H pylori antigen in stool in a large cohort of children compared with invasive diagnostic methods and the (13)C urea breath test.

Patients and methods: A total of 302 symptomatic previously untreated children (aged 0.5-18.7 years; 148 girls) were recruited at three centres. H pylori status was defined by results of culture, histology, the rapid urease test, and the (13)C urea breath test. Stool samples were investigated locally by the EIA using two different production lots. According to the manufacturer's recommendations, an optical density (OD) of 0.150 was used as a cut off value.

Results: OD values clearly differentiated between the 92 H pylori infected and the 210 non-infected children (median (5th-95th percentiles) 2.729 (0.232->4.000) v 0.021 (0.009-0.075)). Only two false positive and two false negative results occurred, giving a sensitivity, specificity, positive predictive value, and negative predictive value of 98%, 99%, 98%, and 99%, respectively. No significant relation was found between age and OD values in infected or non-infected children.

Conclusions: The monoclonal stool antigen EIA was excellent in diagnosing H pylori infection in symptomatic children. Accuracy was independent of the laboratory, production lot used, or the child's age. Because only 18/116 children <6 years of age were infected with H pylori, further validation of the test is needed in young infected children.

Figure 1

Optical density (OD) values in relation to age in 92 children with a positive Helicobacter pylori status. The cut off value was set at an OD of 0.150.

Figure 2

Optical density (OD) values on a log scale in relation to age in 210 children with a negative Helicobacter pylori status. The cut off value was set at an OD of 0.150.