[Stool antigen test for initial Helicobacter pylori diagnosis and for confirmation of eradication after therapy]

Abstract

Background: : Recently, a new diagnostic method based on the detection of Helicobacter pylori antigen in stools (HpSA) has been developed. Our aim was to prospectively evaluate the accuracy of HpSA both in the initial diagnosis of H. pylori infection and in the confirmation of the eradication after treatment.

Patients and method: Thirty dyspeptic patients were prospectively evaluated. During endoscopy, biopsies for histology and rapid urease test were obtained, and a 13C-urea breath test was performed. HpSA was determined by radioimmunoassay(Premier Platinum HpSA). Infected patients were administered H.pylori eradication treatment, and breath test and HpSA were performed again 4 weeks after finishing the therapy. Gold standard for H. pylori infection pre-treatment was based on rapid urease test, histology and breath test, whereas 13C-urea breath test was considered the post-treatment gold standard.

Results: Pre-treatment H. pylori prevalence was 57%. Eradication was achieved in 85% of patients. The area under ROC curve for HpSA pre-treatment was 0.98. Cut-off points with best pre-treatment diagnostic accuracy were those between 0.10 and 0.12: positive likelihood ratio (LR), negative LR, 0.06; 94% sensitivity (95% CI, 73-99%),100% specificity (75-100%), 100% positive predictive value (81-100%)and 93% negative predictive value (66-100%). After treatment,the area under ROC curve was 1, and all cut-off points between 0.10 and 0.18 had 100% diagnostic accuracy. HpSA levels decreased from 0.94 (0.9) to 0.08 (0.02) (p < 0.01) in patients withH. pylori eradication success.

Conclusions: HpSA test can be considered an accurate, non-invasive method for the diagnosis of H. pylori infection both inuntreated patients and in the confirmation of H. pylori eradication after treatment.