High sensitivity and specificity of a laboratory-based serological test, pylori DTect ELISA, for detection of Helicobacter pylori infection

A number of commercial ELISA kits are now available for detection of Helicobacter pylori infection. Generally, whereas the manufacturers have claimed high sensitivity and specificity, independent studies have often failed to confirm the results. The aim of this study was to independently evaluate the pylori DTect ELISA, a commercial kit for detection of H. pylori infection, in Australian patients with dyspepsia and reflux symptoms. Two hundred and nine consecutive patients (102 males and 107 females, mean age 52.8 years) who were referred for endoscopy due to upper gastrointestinal symptoms, but had not received anti-H. pylori therapy were enrolled. A 10 mL blood sample was obtained from each subject and used to evaluate the kit. The absorbance index (AI) was calculated from the mean of two readings of optical density (OD) of each serum sample. Eight biopsies from the gastric antrum (x3), body (x2), fundus (x2), and incisura (x1) were obtained from each patient for CLO-testing (x1), culture (x3), and histological examination (x4) for H. pylori. Overall, 84 (40.2%) patients were infected with H. pylori as determined by the biopsy-based "gold standard." The AIs ranged from 0 to 1.86; 0.12 to 1.86 in H. pylori positive patients and 0 to 1.49 in negative patients. The pylori DTect ELISA obtained an accuracy of 94 to 95% under AI ranges between 0.20 to 0.40, with the highest accuracy being 95% under AIs of 0.25 and 0.35. An AI of 0.25 was recommended as the best cut-off AI, with a sensitivity of 96.4%, specificity of 93.6%, positive predictive value of 91% and negative predictive value of 97.5%. It is concluded that the pylori DTect ELISA is accurate for detecting H. pylori infection in patients with dyspepsia and reflux symptoms in Australia, when an AI of 0.25 is taken as the cut-off value.