gastrointestinal disorders
Helicobacter pylori Infection
Diagnosis ofH. pyloriInfection
Ureabreath testing and stool antigen testing Screening of asymptomatic patients is not warranted. Tests are done during evaluation for peptic ulcer and gastritis. Posttreatment testing is typically done to confirm eradication of the organism. Laboratory and office-based serologic assays for antibodies toH. pylorihave a sensitivity and specificity of>85% and previously were considered the noninvasive tests of choice for initial documentation ofH. pyloriinfection. However, as the prevalence of infection has declined, the percentage of false-positive results with serologic assays has increased significantly, making these tests too unreliable in most countries and regions. As a result,ureabreath testing and stool antigen testing are preferred for initial diagnosis. Qualitative assays remain positive for up to 3 years after successful treatment and because quantitative antibody levels do not decline significantly for 6 to 12 months after treatment, serologic assays are not usually used to assess cure. Ureabreath testsuse an oral dose of 13C- or 14C-labeledurea. In an infected patient, the organism metabolizes theureaand liberates labeled CO2, which is exhaled and can be quantified in breath samples taken 20 to 30 minutes after ingestion of theurea. Sensitivity and specificity are>95%.Ureabreath tests are well suited for confirming eradication of the organism after therapy. False-negative results are possible with recent antibiotic use or concomitant proton pump inhibitor therapy; therefore, follow-up testing should be delayed≥4 weeks after antibiotic therapy and 1 week after proton pump inhibitor therapy. H2 blockers do not affect the test. Stool antigen assayshave a sensitivity and specificity similar to that ofureabreath tests, particularly for initial diagnosis; an office-based stool test is not yet available. Molecular tests for antimicrobial resistance inH. pylorihave been developed and are available in Europe. Endoscopy is used to obtain mucosal biopsy samples for a rapid urease test (RUT) or histologic staining. Bacterial culture is of limited use because of the fastidious nature of the organism. Endoscopy is not recommended solely for diagnosis ofH. pylori; noninvasive tests are preferred unless endoscopy is indicated for other reasons. The RUT, in which presence of bacterial urease in the biopsy sample causes a color change on a special medium, is the diagnostic method of choice on tissue samples. Histologic staining of biopsy samples should be done for patients with negative RUT results but suspicious clinical findings, recent antibiotic use, or treatment with proton pump inhibitors. RUT and histologic staining each have a sensitivity and specificity of>90%. Immunohistochemistry is routinely used in some hospital systems and adds to the value of histology because it can be used to detect a very small number of organisms. 