Stool antigen testing for the diagnosis and confirmation of eradication of Helicobacter pylori infection: a prospective blinded trial.
OBJECTIVE
Helicobacter pylori is an established pathogen for a wide spectrum of gastroduodenal diseases. We investigated the usefulness of H. pylori stool antigen test (HpSA) before and after eradication therapy on patients referred for gastroscopy.


METHODS
Over a 12-month period, 127 adult patients (47% males) underwent HpSA and gastroscopy with dual biopsies from the antrum and proximal body of the stomach for urease and histology. The positive patients (histology, urease or combined positive) received triple therapy consisting of clarithromycin 500 mg, amoxycillin 1 g and omeprazole 20 mg, each given twice daily for 7 days. Six weeks post-therapy, eradication was verified with the 13C-urea breath test (UBT) and the HpSA results compared on a second stool sample.


RESULTS
Pre-therapy, 23/113 patients were positive by urease test, 22/112 by histology and 22/112 were combined positive. For the HpSA, compared to combined urease and histology as the reference standards, the sensitivity and specificity were 79 and 92% while the positive and negative predictive values (PPV and NPV) were 68 and 96%, respectively. Post-therapy, UBT was adopted as the reference standard and 18 paired samples were available for analysis: three were positive and 15 were negative. Sensitivity and specificity were 67 and 100% while the PPV and NPV were 100 and 94%, respectively.


CONCLUSIONS
In this prospective study, HpSA was found to be a reasonably useful diagnostic test for H. pylori infection. Post-eradication, it was highly specific and similar to UBT in terms of PPV and NPV. The test is non-invasive and cheaper than the urease test or the UBT, making it a candidate in the investigation of dyspepsia.
Islam
S
S
Gastroenterology Department, Waikato Hospital, Hamilton, New Zealand. sam.islam@ccdhb.org.nz
Weilert
F
F
Babington
R
R
Dickson
G
G
Smith
A C
AC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D000942:Antigens, Bacterial / Q000032:analysis*; D005243:Feces / Q000382:microbiology*; D005260:Female; D005500:Follow-Up Studies; D005773:Gastroscopy; D016481:Helicobacter Infections / Q000175:diagnosis* / Q000188:drug therapy; D016480:Helicobacter pylori / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies
D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial