Bacteriology High sensitivity and specificity of a laboratory-based serological test, pylori DTect ELISA, for detection of Helicobacter pylori infection Harry Hua-Xiang Xia a , Jamshid S. Kalantar a , Jenny Ma Wyatt b , Stuart Adams b , Karen Cheung b , Guy D. Eslick a , Nicholas J. Talley a, * a Department of Medicine, The University of Sydney, Nepean Hospital b Department of Anatomical Pathology, Nepean Hospital, NSW 2751, Australia Received 19 May 1999; revised and accepted 1 September 1999 Abstract 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 (3), body (2), fundus (2), and incisura (1) were obtained from each patient for CLO-testing (1), culture (3), and histological examination (4) 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. © 2000 Elsevier Science Inc. All rights reserved. 1. Introduction Serological diagnosis of Helicobacter pylori infection is a major non-invasive diagnostic tool in epidemiologi- cal studies (Talley et al., 1991; Mitchell et al., 1988; Huang et al., 1998). In recent years, H. pylori serology has also been applied to screen patients with dyspepsia before endoscopy and may have a role in long term monitoring after antimicrobial therapy (Axon et al., 1995; Thijs et al., 1996; Sobala et al., 1991; Sheu et al., 1997; Veenendaal et al., 1991; Cutler and Prasad, 1996). Serology is cheaper and more accessible than 13 C- or 14 C-urea breath testing, which is also a noninvasive test commonly used for the diagnosis of H. pylori. Enzyme- linked immunosorbent assays (ELISAs) remain the most commonly used serological method for the detection of H. pylori infection, and several commercial ELISA kits are now available (Talley et al., 1991; Mitchell, 1997; Graham et al., 1996; Loy et al., 1996; Laheij et al., 1998). However, studies of the sensitivity and specificity of these tests have produced inconsistent results (Talley et al., 1991; Mitchell, 1997; Graham et al., 1996; Loy et al., 1996; Laheij et al., 1998). Whereas the manufacturers of many of these tests have claimed high sensitivity and specificity, independent studies have often failed to con- firm these results (Mitchell, 1997). Recently, a new kit, pylori DTect ELISA, has been developed in Australia. Preliminary evaluations conducted by the manufacturer on 263 subjects have suggested that this new test is highly sensitive (96%) and specific (93%) (unpublished data in the instruction manual). The aim of this study was to independently evaluate the pylori DTect ELISA for the detection of H. pylori infection in Australian patients with dyspepsia and reflux symptoms. * Corresponding author: Tel.: +61-2-47-242613; fax: 461-2-47- 242614 E-mail address: ntalley@med.usyd.edu.au (N.J. Talley) Diagnostic Microbiology and Infectious Disease 36 (2000) 69 –74 0732-8893/00/$ – see front matter © 2000 Elsevier Science Inc. All rights reserved. PII: S0732-8893(99)00101-7