The effect of dosing with omeprazole on the accuracy of the 13C-urea breath test in Helicobacter pylori-infected subjects

Background : The 13C-urea breath test (13C-UBT) is an accurate means of Helicobacter pylori diagnosis. However, proton pump inhibitors may suppress H. pylori and cause false negative results. Aim : To study the kinetics of H. pylori suppression by omeprazole during and after short-term use. Methods : Volunteers underwent a baseline 13C-UBT (13C-urea 100 mg). H. pylori-positive subjects took omeprazole 20 mg daily for 14 days. Those who remained 13C-UBT positive (δ13CO2 ≥ 5) continued omeprazole for a further 14 days. 13C-UBTs were performed weekly on omeprazole and then every second day after it was stopped. False negatives occurred when δ13CO2 fell to < 5. Results : In 25 H. pylori-positive subjects (mean age 43.9 ± 2.4 years; 21 females, 4 males) the mean baseline δ13CO2 was 28.1 ± 3.4. False negative breath tests occurred in three subjects after 7 days of omeprazole and in a further four subjects after 14 days. A further six subjects developed negative tests between Days 14 and 28. Following cessation of omeprazole, the 13C-UBT became positive again in 12/13 subjects within 4 days and in all within 6 days, with a mean recovery to 99.9 ± 18.6% of baseline δ13CO2. Conclusions : False negative 13C-UBTs are common during treatment with omeprazole and occur after as little as 7 days. Return to positive test results is rapid after cessation of omeprazole. These findings are relevant to the timing of testing in clinical practice.