Eficacia de la determinación fecal de Helicobacter pylori mediante la técnica HpSA en enfermos con hemorragia digestiva alta

Abstract

The rapid urease test is the most commonly used test in the diagnosis of Helicobacter pylori infection in patients with upper gastrointestinal hemorrhage. However, some studies have suggested that results of this test are frequently false negative when blood is present. An effective new enzyme immunoassay for determining H. pylori antigens in stools has recently begun to be used. To determine the efficacy of the H. pylori stool antigen test (HpSAT) in patients with upper gastrointestinal hemorrhage. Thirty-two patients with upper gastrointestinal hemorrhage were prospectively studied from November 1998 to April 1999. In all patients the following tests were performed in the first 72 hours after onset of bleeding and 24 hours after hospital admission: upper gastrointestinal endoscopy, biopsy samples for the rapid urease test and histological study, blood samples for serology, stool samples for HpSAT, and the 13C urea breath test. Criteria for infection was a positive result in at least two of the four diagnostic techniques, except in the case of HpSAT. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated. Of the 32 patients, 23 (71.8%) were infected. The results of four HpSAT (12.5%) were negative and 28 were positive (87.5%). HpSAT showed high sensitivity (95.6%) but low specificity (33.3%). The PPV and NPV were 78.5% and 75% respectively. Of the 32 HpSAT, 25 (78.1) were performed in melenic stools: 22 were positive and 3 were negative. Seventy-five percent of negative HpSAT and 78.5% of positive HpSAT corresponded to melenic stools. HpSAT is a rapid, non-invasive technique that does not appear to be influenced by the presence of blood. Consequently, it can be applied in patients with upper gastrointestinal hemorrhage. The rapid urease test showed high sensitivity, specificity and PPV and should remain the first-line test in patients with upper gastrointestinal hemorrhage. HpSAT is appropriate as a second-line technique and is useful when the rapid urease test is negative and infection is strongly suspected, when no samples for the rapid urease test have been taken and when endoscopy cannot be performed. The result obtained in the present study should be confirmed in future studies with larger samples.