Background: Rapid non-invasive diagnostic tests that can reliably document the presence or absence of Helicobacter pylori infection are urgently required. The aim of this study was to determine the accuracy of two immunoassays (Flex-Sure and MedMira), developed for use outside the laboratory setting by practitioners, in the setting of a low prevalence of H. pylori infection.
Methods: Serum samples collected in four previous studies (n = 349) were employed to detect the presence of H. pylori-specific immunoglobulin G, compared to previous results obtained using endoscopic biopsies, serology, flow cytometry, and urease breath testing. Serum samples included 52 obtained from adults (parents and grandparents of symptomatic children), 123 sera collected from children and adolescents undergoing diagnostic upper endoscopy for upper gastrointestinal tract symptoms, and 174 samples drawn from children in the primary care setting with or without recurrent abdominal pain.
Results: Overall, 16% of subjects were infected by the gastric pathogen. Both the specificity (%) and negative predictive value (%) of the two tests were high (FlexSure: 91 and 92; Medmira: 97 and 94, respectively). In adults, both tests also demonstrated high sensitivity (83% and 86%) and positive predictive values (79% and 83%, respectively). However, in children where the prevalence of infection was 12% (37 of 297 subjects), the sensitivity (59% and 71%) and positive predictive values (55% and 88%, respectively) of the immunoassays were lower.
Conclusions: These findings indicate that, in the setting of a low prevalence of H. pylori infection, the MedMira office-based test provides satisfactory results and utility. However, the low positive-predictive value of the FlexSure kit may limit applicability of this test in children.