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H. Pylori Eradication Based on Stool Antigen Testing

Diagnostic Tests for H. Pylori Infection Indirectly identify bacteria Antibody test in urine, blood, or saliva Direct tests that identify the entire organism Histology and culture Antigen testing Stool antigen test Metabolic functions of the organism Rapid urease testing Urea breath test H. pylori = Helicobacter pylori.

Eradication of Helicobacter pylori is a common management strategy in patients with dyspepsia who have no symptoms suggestive of more serious pathology. Post-therapy confirmation of bacterial eradication is important because of the growth of resistant H. pylori strains and the continuation of symptoms that may occur with incomplete eradication. Most of the tests currently available to document post-treatment eradication of H. pylori (see the accompanying table) are inadequate. Serologic testing is unreliable, and endoscopic sampling is expensive and inconvenient. Although the urea breath test is reliable, it can only be used four weeks after treatment and is not widely available. Vaira and associates conducted a prospective, blinded study to determine if the fecal antigen test can reliably identify the presence of H. pylori infection that persists despite eradication efforts.

The fecal antigen test is currently approved by the U.S. Food and Drug Administration for detection of H. pylori before and after treatment. Eighty-one patients with dyspepsia and endoscopically obtained positive histologic specimens or culture completed the study. They were treated with one of the commonly approved eradication regimens. Stool for antigen testing was collected at intervals and on completion of therapy. On day 35 after completion, endoscopic biopsy specimens were again obtained for analysis with histology, culture, and the rapid urease test. Compared with the gold standard endoscopic test on day 35, stool antigen tests had a probability of accurately predicting persistent infection on day 7.

The authors conclude that although current standards recommend using the urea breath test four weeks after completion of treatment, stool antigen testing seven days after completion of treatment provides reliable estimations of patients in whom eradication of H. pylori is incomplete. Stool antigen concentrations decrease rapidly when treatment is successful and increase when eradication has failed. Stool antigen testing can identify treated patients who are still infected.

RICHARD SADOVSKY, M.D.

Vaira D, et al. The stool antigen test for detection of Helicobacter pylori after eradication therapy. Ann Intern Med February 19, 2002;136:280-7.