The impact of short-term ranitidine use on the precision of the 13C-urea breath test in subjects infected with Helicobacter pylori

Background The C-13-urea breath test (C-13-U BT) is a very accurate method of Helicobacter pylori diagnosis with a false-negative rate of 1-3%. However, the accuracy of the C-13-UBT is affected by potent acid inhibition with proton-pump inhibitors, which may suppress H. pylori and cause false-negative results. It is not known whether this occurs with less potent acid inhibition by H-2-antagonists and any effect may be important clinically. Objective To determine the kinetics of (CO2)-C-13 excretion in H. pylori infected subjects during and after short-term ranitidine use. Methods Volunteers underwent a baseline C-13-UBI (positive: delta(13)CO(2) greater than or equal to 5.0; negative: less than or equal to 3.5; indeterminate: > 3.5 to < 5,0), Infected subjects took ranitidine 300 mg each evening for up to 28 days. C-13-UBTs were performed at weekly intervals and then every other day after ranitidine was ceased. If the C-13-UBT remained positive after 14 days, ranitidine was continued for a further 14 days. Results Thirty-one subjects were studied (mean age 40.4 +/- 2.1 years; 23 female/8 male; mean baseline delta(13)CO(2) 27.3 +/- 2.5). In 28 subjects the C-13-UBT remained positive during ranitidine use. The mean delta(13)CO(2) rose to 124% (P < 0.06) and 121% (P < 0.05) of baseline at 14 and 28 days respectively. In two subjects, the delta(13)CO(2) became indeterminate at day 7 (delta(13)CO(2) 4.3 and 3.8). In one of these, return to a positive value (delta(13)CO(2) 13.6; 103% of baseline) occurred while still on ranitidine. The other subject became positive again by day 3 off ranitidine (17.8; 119% of baseline). One subject had a transiently negative test after 21 days and this became positive again while still taking ranitidine. Conclusions Ranitidine has a minimal effect on the C-13- UBT. The rate of indeterminate or false-negative tests is no greater than in patients on no anti-secretory medication. Eur J Gastroenterol Hepatol 11:1135-1138 (C) 1999 Lippincott Williams & Wilkins.