Diagnosis of Helicobacter pylori infection: validation of a commercial non invasive salivary test against urea breath test and serology.

BACKGROUND Helicobacter pylori (H. pylori) infection plays an important role in the pathogenesis of chronic gastritis, peptic ulcer disease, MALT lymphoma and gastric cancer. Recently Helicobacter spp. infection has been correlated with cirrhosis, hepatocellular carcinoma and acute myocardial infarction. Several invasive and non-invasive tests have been proposed for the detection of the bacterium. In clinical practice, the selection of the appropriate test will depend on the disease and on cost-effectiveness. Aim of the study was to validate a rapid, salivary test for detecting the presence of antibodies against H. pylori in a population of patients undergoing to the 13C-urea breath test (13C-UBT). METHODS Saliva and serum samples were obtained from 91 patients (47 females, mean age 53+/-6.7 years) attending the 13C-UBT service between 15 September and 31 November 1999. Thirty-five of them had had a previous diagnosis of peptic ulcer at endoscopy and 46 out of 91 had a diagnosis of histologically confirmed chronic gastritis. 39 out of 91 were dyspeptic patients with no symptoms suspect for peptic ulcer or cancer. Patients were excluded from the 13C-UBT if they had been treated with inhibitors of acid secretion and antibiotics within 30 days before testing. Breath sample were collected at baseline and 30 minutes after the ingestion of orange juice and a 75 mg dose of 13C-labeled urea. The presence in serum of antibodies (IgG) against the bacterium was assessed by means of a commercial enzyme immunosorbent assay with a reported sensitivity of 94% and specificity of 87%. Saliva was collected using a sterile absorbent pad placed between the mandibular gum and the cheek in the mouth and assayed for H. pylori antibodies by an immunochromatographic rapid method. RESULTS Thirty-seven of the 91 patients were defined positive by 13C-UBT and serological test. Twenty-nine of these 37 were identified as positive by the salivary test. Fifty-four patients were defined as negative but the salivary test identified 13 of them as positive, thereby sensitivity and specificity were 78.3 and 75.9% respectively. The accuracy was 76.9%. Positive predictive value was 69% and negative predictive value 83.6%. CONCLUSIONS The salivary test could be considered in the ambulatory setting, as a non-invasive tool for the screening of H. pylori infection, when more accurate methods are not available.