What are the instructions for a breath test for H. pylori infection?

H. Pylori Urea Breath Test Instructions

The urea breath test requires patients to fast for at least 6 hours before testing, discontinue proton pump inhibitors for at least 2 weeks prior, and stop antibiotics and bismuth for at least 4 weeks to avoid false-negative results. 1, 2

Pre-Test Preparation

Medication Discontinuation

• Stop proton pump inhibitors (PPIs) for at least 2 weeks (ideally 7-14 days) before testing, as they cause 10-40% false-negative rates by decreasing bacterial load in the stomach 2
• Discontinue antibiotics and bismuth for at least 4 weeks before the test to prevent false-negative results 1, 2
• H2-receptor antagonists can be substituted for PPIs during the waiting period, as they do not significantly affect bacterial load 1

Fasting Requirements

• Fast for at least 6 hours before the urea breath test 2
• However, research demonstrates that a light meal (two slices of toast with jam or honey and tea or coffee) does not reduce test accuracy, with 98% sensitivity and 96% specificity maintained 3

Test Procedure

Administration Protocol

• Patient ingests labeled urea (either 13C-urea or 14C-urea) with a test meal to delay gastric emptying and allow even distribution throughout the stomach 1
• Modern tablet formulations of 13C-urea are preferred as they avoid interference from urease-producing bacteria in the oropharynx that can cause false-positive results 1
• Doses of 75 mg of 13C-urea have proven as accurate as higher amounts while being less expensive 1

Sample Collection Timing

• Baseline breath sample is collected before urea ingestion 1
• Second breath sample collected 10-30 minutes after ingestion, depending on the protocol used 1
  • Newer tablet formulations allow sampling as early as 10 minutes with excellent accuracy 1
  • Traditional protocols require sampling at 20-30 minutes 1, 4

Test Accuracy and Interpretation

Diagnostic Performance

• The urea breath test demonstrates superior accuracy with weighted mean sensitivity of 94.7% and specificity of 95.7% based on analysis of 3,643 patients 2
• Sensitivity and specificity range from 95-100% across multiple studies 5, 6

Critical Timing Considerations

• For post-treatment testing, wait at least 4 weeks after completion of H. pylori therapy before performing the breath test to allow gastric mucosa to recover and avoid false-negative results 1, 7
• Testing performed before 4 weeks may show false-negative results due to temporary bacterial suppression rather than true eradication 7

Common Pitfalls to Avoid

False-Negative Results

• PPI use is the most common cause of false-negative results - ensure 2-week discontinuation minimum 2, 8
• Research shows that 33% of patients taking lansoprazole had false-negative breath tests, with results reverting to positive 7-14 days after stopping the medication 8
• Testing too soon after treatment (before 4 weeks) will produce unreliable results 7

False-Positive Results

• Oropharyngeal urease-producing bacteria can cause false-positives with liquid urea formulations, which is why tablet formulations are preferred 1

Important Clinical Notes

• A positive result can be trusted even if the patient is on PPIs or antibiotics, as these medications only cause false-negatives, not false-positives 1
• If doubt exists about a false-negative result, repeat the test after at least 2 weeks off interfering medications 1