Evaluation of Test Results

Test Method

The ratio of ¹³CO₂ to ¹²CO₂ in breath samples is determined by Infrared Spectrophotometry.

Diagnostic Criteria

We determine the Delta Over Baseline for each urea breath test (UBT). Delta Over Baseline (DOB) is the difference between the ratio (¹³CO₂ / ¹²CO₂) in the Post-Dose sample and the corresponding ratio in the Baseline sample. The diagnostic criteria for a positive UBT result (presence of H. pylori) is a DOB of 2.4 or higher. A result less than 2.4 DOB is interpreted as diagnostically negative indicating the absence of H. pylori. This diagnostic criteria was determined in a controlled study of sixty-six infected and fifty-three uninfected asymptomatic, apparently healthy volunteers.

The 2.4 DOB cutoff point applies to both initial diagnosis and post-treatment monitoring of H. pylori infection. A correlation between the number of H. pylori organisms in the stomach and the urea breath test result has not been established.

Causes of False-Negative Results

False-negative results may occur if the patient does not fast for at least one (1) hour before administering the urea breath test. False negative results can also occur if patients take antimicrobials, proton pump inhibitors, or bismuth preparations within two (2) weeks prior to the urea breath test. Premature Post-Dose breath colletion time can lead to a false negative diagnosis for a patient with a marginally positive UBT result.

A negative result does not rule out the possibility of H. pylori infection. Although rare (2-5%), false negative results do occur with this procedure. If clinical signs are suggestive of H. pylori infection, retest patient.

Patients should not be tested for four (4) weeks after H. pylori treatment. An earlier post-treatment assessment may give false negative results.

Causes of False-Positive Results

False-positive results are almost always the result of improper test preparation or conduct. Patients need to avoid eating for at least one (1) hour before administering the urea breath test. A false-positive test may occur due to urease associated with other gastric spiral organisms observed in humans. Another potential cause, although remote, of false-positve results is the presence of achlorhydria in patients.

For more information about the performance characteristics of the BreathTek UBT, consult the package insert.