Stool antigen assay (HpSA) is less reliable than urea breath test for post-treatment diagnosis of Helicobacter pylori infection.
BACKGROUND
The diagnostic yield of the stool antigen test (HpSA) in evaluating the results of Helicobacter pylori eradication therapy is controversial, but many studies have used only the 13C-urea breath test (13C-UBT) as a gold standard which has greatly reduced their relevance.


OBJECTIVE
To compare the reliability of HpSA and 13C-UBT in patients post-treatment using biopsy-based methods as reference tests.


METHODS
A total of 100 consecutive dyspeptic patients (42 male and 58 female; mean age, 56 +/- 18 years) were enrolled in our study. All patients were H. pylori positive on the basis of at least two biopsy-based methods, and underwent 1 week of treatment with various triple therapies. They were again endoscoped 4 weeks after completing therapy and six biopsy specimens were taken from the gastric antrum and corpus for rapid urease test, histology and culture. HpSA and 13C-UBT were also performed within 3 days of the second endoscopy.


RESULTS
On the basis of biopsy-based tests, infection was eradicated in 77 patients but continued in 23. Three false negatives were observed with HpSA and two with 13C-UBT. In contrast, the number of false positives was significantly higher (P < 0.01) with HpSA than with 13C-UBT (nine vs. one), confirming the lower specificity of the former test. The overall accuracy of HpSA was 88% vs. 97% for 13C-UBT (P < 0.02).


CONCLUSIONS
HpSA has lower diagnostic value than 13C-UBT in the evaluation of the outcome of anti-H. pylori therapy. 13C-UBT remains the first-line diagnostic method to monitor eradication results. The use of HpSA should be reserved for those settings in which 13C-UBT is not available.
Bilardi
C
C
Dipartimento di Medicina Interna e Specialità Mediche, Università di Genova, Italy.
Biagini
R
R
Dulbecco
P
P
Iiritano
E
E
Gambaro
C
C
Mele
M R
MR
Borro
P
P
Tessieri
L
L
Zentilin
P
P
Mansi
C
C
Vigneri
S
S
Savarino
V
V
D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D000942:Antigens, Bacterial / Q000032:analysis*; D001706:Biopsy; D001944:Breath Tests / Q000379:methods; D002247:Carbon Isotopes; D004359:Drug Therapy, Combination; D005243:Feces / Q000382:microbiology*; D005260:Female; 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; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial; D002247:Carbon Isotopes