Diagnosis of Helicobacter pylori infection by stool antigen determination:A systematic review

Recently a new, noninvasive diagnostic test based on the detection of Helic obacter pylori stool antigen (SA) has been developed. The aim of this study was to systematically review the experience on H. pylori SA test for the d iagnosis of H. pylori infection. Bibliographic searches were performed in t he PubMed database and abstracts from several congresses. A total of 43 stu dies fulfilled the inclusion criteria and evaluated H. pylori SA test accur acy for the diagnosis of H. pylori infection in nontreated patients. Overal l, 4769 patients were included. The sensitivity, specificity, positive pred ictive value (PPV) and negative predictive value (NPV) (weighted mean) were , respectively: 92.4% (95% CI = 91-93%), 91.9% (91-92%), 92.1% (91-93%), an d 90.5%n (90-91%). Therefore the SA test can definitively be considered an accurate noninvasive method for the diagnosis of H. pylori infection in unt reated patients. A total of 25 studies including 2078 patients evaluated H. pylori SA test for the confirmation of H. pylori eradication greater than or equal to4 wk after completion of therapy. Sensitivity, specificity, PPV and NPV (weighted mean) were: 88.3% (87-90%), 92% (91-93%), 75.1% (73-77%), and 94.8% (94-96%). Although most studies showed that SA test is an accura te method to confirm H. pylori eradication greater than or equal to4 wk aft er treatment, these favorable results were not confirmed in other studies. Further investigation is necessary to explain these discrepancies, as well as to clarify the precise time for confirmation of eradication after therap y, the appropriate cutoff point for the SA test, and which factors influenc e it. Proton pump inhibitors seem to affect the accuracy of SA test, but th e negative effect disappears 1-2 wk after stopping treatment. The SA test i s technically feasible in patients with upper GI bleeding, although the tru e diagnostic accuracy in this group of patients remains to be more fully as sessed. Finally, the SA test seems to be a highly cost-effective method for the diagnosis of H. pylori infection. (Am J Gastroenterol 2001;96:2829-283 8. (C) 2001 by Am. Coll. of Gastroenterology).