Volume 2 • Supplement 1 • 1997 HELICOBACTER © Blackwell Science, Inc. 1083-4389/97/$10.50/34 S-34–S-37 S-34 Urea Breath Tests for the Detection of Helicobacter pylori Infection Franco Bazzoli, Maurizio Zagari, Stefania Fossi, Paolo Pozzato, Luigi Ricciardiello, Constance Mwangemi, Aldo Roda, and Enrico Roda ABSTRACT Dipartimento di Medicina Interna e Gastroenterologia, Università di Bologna, Bologna, Italy Background. Helicobacter pylori is recognized as an important human pathogen. The urea breath test, using either 13 C or 14 C, provides a noninvasive diagnostic method for the detection of active H. pylori infection. Methods. We review the data regarding the utility of the urea breath test in the diagnosis and follow-up of patients with suspected H. pylori infection. Results. Following its ingestion, labeled urea is hydro- lyzed by H. pylori urease, producing ammonia and la- beled CO 2 , which is absorbed and can be detected in expired breath. The urea breath test provides a semi- quantitative assessment of the load of H. pylori and overcomes the problem of the sampling error due to the patchy distribution of the infection. 13 C-urea breath test has an advantage over the 14 C version, because the 13 C isotope is a nonradioactive natural isotope; therefore, a user’s license is unnecessary, making simple the han- dling and mailing of samples. The 13 C-urea breath test is preferred in children and expectant mothers. Conclusion. The high sensitivity, and specificity of the 13 C-urea breath test are such that it can be considered a clinical gold standard against which other diagnostic methods can be validated. This test can be used as the sole method for evaluating the effectiveness of treat- ment of H. pylori infection. T he basics of the urea breath test (UBT) is the rapid hydrolysis of labeled urea (with 13 C or 14 C) by the urease produced by H. pylori [1,2]. La- beled CO 2 diffuses into the bloodstream and is ex- creted in the expired breath. The measurement of labeled CO 2 in a single, pooled, or serial sample indicates the presence or absence of Helicobacter pylori infection. 14 C-Urea Breath Test The widespread availability of scintillography for 14 CO 2 analysis and the lower cost of 14 C might make the 14 C-UBT appear an attractive alternative to the 13 C-UBT [3,4]. However, even minimal risk of radiation exposure renders the use of 14 C-UBT inappropriate in children and pregnant women. Though the ingested dose of 14 C is very low, the long half-life of this isotope makes its extensive use questionable. Moreover, special storage facili- ties for radioactive waste are required and, in some European states, there are laws prohibiting the use of radioactive materials when equivalent stable isotopes are available. Ultimately, there are no standard protocols for the 14 C-UBT, thereby making necessary further validation studies. 13 C-Urea Breath Test 13 C is a stable isotope and therefore is completely safe and can be used without restriction or need for a user’s license or special storage facilities [5– 7]. Consequently, the majority of UBT research has been conducted using 13 C-urea. Collaborating European investigators have been encouraged by the European Union’s wish to promote the use of stable isotopes in clinical research. The major dis- advantage to the 13 C-UBT is the capital cost of equipment for centers that want to perform the analysis in-house. The volume of expired CO 2 is not critical for the analysis of 13 CO 2 , because 13 C is always mea- sured as a ratio relative to 12 C. The 13 C/ 12 C ratio (  ) usually is expressed as parts per thousand (per mil) relative to an international primary standard, PDB (Pee Dee Belemnite) calcium carbonate [8]. The background excretion of 13 CO 2 in the expired Reprint requests to: Franco Bazzoli, M.D., Associate Pro- fessor of Medicine, Dipartimento di Medicina Interna e Gastroenterologia, Università di Bologna, Policlinico S. Orsola, Via Massarenti, 9, 40138 Bologna, Italy. Email ad- dress: bazzoli@alma.unibo.it.