Tests Done In The Diagnosis Of Helicobacter pylori Infection

A 54-year-old man is investigated for dyspepsia. An endoscopy shows a gastric ulcer and a CLO test (rapid urease test) done during the procedure demonstrates H. pylori infection. A course of H. pylori eradication therapy is given. Six weeks after completing treatment the patients comes for review. Unfortunately his symptoms have not improved. What is the most appropriate test to confirm H. pylori eradication?

A. Culture of gastric biopsy
B. H. pylori serology
C. Hydrogen breath test
D. Urea breath test
E. Stool culture

Answer:
D. Urea breath test

Discussion: It is important to remember that H. pylori serology remains positive following eradication. A stool antigen test, not culture, may be an appropriate alternative.

Tests Done In The Diagnosis Of  Helicobacter pylori  Infection: 

Urea breath test 
 patients consume a drink containing carbon isotope 13 (13C) enriched urea
 urea is broken down by H. pylori urease
 after 30 mins patient exhale into a glass tube
 mass spectrometry analysis calculates the amount of 13C CO2
 should not be performed within 4 weeks of treatment with an antibacterial or within 2 weeks of an antisecretory drug (e.g. a proton pump inhibitor)
 sensitivity 95-98%, specificity 97-98%

Rapid urease test (e.g. CLO test) 
 biopsy sample is mixed with urea and pH indicator
 colour change if H pylori urease activity
 sensitivity 90-95%, specificity 95-98%

Serum antibody 
 remains positive after eradication
 sensitivity 85%, specificity 80%

Culture of gastric biopsy 
 provide information on antibiotic sensitivity
 sensitivity 70%, specificity 100%

Gastric biopsy 
 histological evaluation alone, no culture
 sensitivity 95-99%, specificity 95-99%

Stool antigen test 
 sensitivity 90%, specificity 95%