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AIM: To study the diagnosis of Helicobacterpylori (Hpylori) infection through the determination of serum levels of antiH pylori IgG and IgA antibodies, and the levels of anti-H pylori IgA antibodies in duodenal fluid.METHODS: Data were collected from 93 patients submitted to upper digestive endoscopy due to dyspeptic symptoms.The patients were either negative (group A) or positive (group B) to H pyloriby means of both histological detection and urease tests. Before endoscopy, peripheral blood was collected for the investigation of anti-H pylori IgG and IgA antibodies. To perform the urease test, biopsies were obtained from the gastric antrum. For the histological evaluation, biopsies were collected from the gastric antrum (greater and lesser curvatures) and the gastric body.Following this, duodenal fluid was collected from the first and second portions of the duodenum. For the serological assaying of anti-H pyloriIgG and IgA, and anti-H pyloriIgA in duodenal fluids, the ELISA method was utilized.RESULTS: The concentration of serum IgG showed sensitivity of 64.0%, specificity of 83.7%, positive predictive value of 82.0%, negative predictive value of 66.6% and accuracy of 73.1% for the diagnosis of H pylori infection. For the same purpose, serum IgA showed sensitivity of 72.0%,specificity of 65.9%, positive predictive value of 72.0%,negative predictive value of 67.4% and accuracy of 69.8%.If the serological tests were considered together, i.e. when both were positive or negative, the accuracy was 80.0%,sensitivity was 86.6%, specificity was 74.2%, positive predictive value was 74.2% and negative predictive value was 86.6%. When values obtained in the test for detecting IgA in the duodenal fluid were analyzed, no significant difference (P = 0.43) was observed between the values obtained from patients with or without H pylori infection.CONCLUSION: The results of serum IgG and IgA tests for H pylori detection when used simultaneously, are more efficient in accuracy, sensitivity and negative predictive value,than those when used alone. The concentration of IgA antibodies in duodenal fluid is not useful in identifying patients with or without H pylori.