Am Fam Physician. 1998;57(7):1646
Helicobacter pylori is well-established as the causative agent in most cases of gastric and duodenal ulcers. H. pylori produces high concentrations of urease, which hydrolyzes urea into ammonium and bicarbonate. The bicarbonate enters the blood stream, is transported to the lungs and is rapidly exhaled as carbon dioxide. Diagnosis of H. pylori infection is typically confirmed by endoscopy with biopsy—a test that is both invasive and expensive. Felz and colleagues evaluated the effectiveness of the carbon 14 urea breath test as a noninvasive and less expensive way of diagnosing H. pylori infection in patients with symptoms of chronic gastritis.
Twenty-six patients with symptoms of gastritis were included in the nonblinded study. All patients underwent upper gastrointestinal endoscopy and biopsy, a CLO (Campylobacter-like organism) test of gastric antral tissue and a 14C-urea breath test. In the breath test, patients first swallowed a 14C-labeled gelatin capsule, and breath samples were obtained 10, 15 and 20 minutes after ingestion of the capsule. Patients exhaled through a straw into a 1.5-L aluminized balloon, and carbon radioactivity was counted in a liquid scintillation counter. Samples were considered positive if they contained more than 100 disintegrations per minute (dpm), indeterminate if they contained 50 to 99 dpm and negative if they contained less than 49 dpm.
Seventeen patients (65 percent) had endoscopic evidence of gastric or duodenal ulceration. Three patients (12 percent) had no visible ulcers but had histologic evidence of H. pylori infection on biopsy, microorganisms on Giemsa stain and positive results on a CLO test. Of these 20 patients, all had strongly positive 14C-urea breath tests, with an average 15-minute reading of 1,868 dpm. The other six patients (23 percent) had no positive findings for ulceration based on the testing parameters of the study. Results of the 14C-urea breath test were negative in five of these patients and indeterminate in one. These results correlate with a sensitivity of 100 percent (20 of 20 positive) and a specificity of 100 percent (six of six negative). Since no diagnostic errors occurred with the breath test, the positive and negative predictive values for this study were also 100 percent.
The authors concluded that the 14C-urea breath test is a noninvasive and very reliable method for diagnosing H. pylori infection in patients with symptoms of duodenal or gastric ulceration or active chronic gastritis. This test is quick, easy and well tolerated by patients. The amount of radiation exposure associated with this test is far less than that received in mammography, an intravenous pyelogram or an upper gastrointestinal series. The estimated cost of the test is about $200.