Urea breath test for the diagnosis of Helicobacter pylori

Abstract

We read with interest the article by Hahn et al.1Hahn M Fennerty M Corless C Magaret N Lieberman DA Faigel DO Non-invasive tests as a substitute for histology in the diagnosis of Helicobacter pylori infection.Gastrointest Endoscopy. 2000; 52: 20-26Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar in a recent issue of Gastrointestinal Endoscopy.1Hahn M Fennerty M Corless C Magaret N Lieberman DA Faigel DO Non-invasive tests as a substitute for histology in the diagnosis of Helicobacter pylori infection.Gastrointest Endoscopy. 2000; 52: 20-26Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar They compare the different invasive and noninvasive methods for the diagnosis of H pylori infection for accuracy and cost. Sixty-seven patients with a negative rapid urease test had a histologic examination of biopsy specimens, a urea breath test (UBT), a whole blood antibody test, and a serology. They found that all tests except histology had a negative predictive value (NPV) of 100% and that the positive predictive value (PPV) of the tests ranged between 50% and 80% except for the UBT and the whole blood antibody test in which the PPV was 31% and 36%, respectively. Histology was the most costly test, followed by UBT and a commercial (send-out) serology. They concluded that whole blood or serum antibody testing is a rapid, accurate, and cost-effective means for establishing H pylori status in rapid urease test-negative patients. We fully agree with these investigators that these tests, based on the presence of antibodies are very accurate. Concerning cost-effectiveness, however, we would like to add two remarks. Because these tests are only useful in a setting of untreated patients, as mentioned in the article, physicians still need to have access to other diagnostic methods. This inevitably increases the general costs. Concerning the UBT, which can be used in treated patients, untreated patients, actively bleeding patients,2Tu TC Lee CL Wu CH Chen TK Chan CC Huang SH et al.Comparison of invasive and noninvasive tests for detecting Helicobacter pylori infection in bleeding peptic ulcers.Gastrointest Endosc. 1999; 49: 302-306Abstract Full Text Full Text PDF PubMed Scopus (96) Google Scholar and patients in whom histologic examination is not possible, the high price is because of the costly mass spectrometer. The development of the lower-priced infrared spectrometry, however, which has the same accuracy as the mass spectrometry,3Savarino V Mela GS Zentilin P Bisso G Pivari M Monsi C et al.Comparison of isotope mass spectrometry and nondispersive isotope selective spectroscopy for 13C-urea breath test.Am J Gastroenterol. 1999; 94: 1203-1208Crossref PubMed Scopus (81) Google Scholar allows a reduction in cost. Concerning the accuracy of the UBT, we acquired clinical experience with infrared spectrometry. We likewise studied the PPV and NPV, comparing them with histologic examination of biopsy specimens taken during endoscopy on the same day. Our results were 93% and 100%, respectively, with a cut-off value of 3.0 0/00 DOB. However, our study population was unselected (biopsy-positive as well as biopsy-negative patients), and the used cut-off value was higher. This could probably explain our better results. The fact that we used only histologic examination of biopsy specimens as the gold standard, however, should lower our PPV. Histologic examination, as confirmed in the study of Hahn et al.,1Hahn M Fennerty M Corless C Magaret N Lieberman DA Faigel DO Non-invasive tests as a substitute for histology in the diagnosis of Helicobacter pylori infection.Gastrointest Endoscopy. 2000; 52: 20-26Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar is the only test with a NPV that is different from 100%. Negative histology in our study thus leads in some cases to a positive UBT, classified as falsely positive. We also believe that a gray zone instead of a clear cut-off is better because the coefficient of repeatability is not zero.4Mana F Franken PH Ham HR Reynaert H Urbain D 13C 13C urea breath test with nondispersive isotope-selective infrared spectrometry: reproducibility and importance of the fasting status.Helicobacter. 2000; 5: 104-108Crossref PubMed Scopus (20) Google Scholar