H pylori breath test

Helicobacter Pylori in the stomach produces urease. The 13C UREA breath test detects the activity of the urease.

The patient ingests 13C-labelled urea and in the presence of urease 13C-labelled carbon dioxide is released in the patient's breath. This stable isotope of carbon can be quantified. A variant of the test uses 14C-labelled urea, in this case the patient exhales radioactive carbon dioxide which can then be detected.

The breath test becomes negative when H.Pylori has been eradicated, unlike the antibody test which remains positive after treatment.

• a patient due to undergo breath testing should not take antibacterial drugs for at least 4 weeks before testing and proton pump inhibitors for at least 2 weeks before testing, as these treatments suppress H. pylori and make a false-negative result more likely
• in a systematic review 13C-urea breath tests were more accurate than serological tests (median sensitivity 96.5% and specificity 96%; vs. 91% and 90%, respectively, for laboratory-based serological tests; vs. 86% and 75.5% for near-patient serological tests) (2)

Reference:

1. Drug and Therapeutics Bulletin 2004; 42(9): 71-2.
2. Roberts AP et al. Tests for Helicobacter pylori infection: a critical appraisal from primary care. Fam Pract 2000; 17 (suppl 2): S12-20.