Effect of Mouth Washing on the C-13 -Urea Breath Test

Background: Mouth washing is often mentioned as a possible method to eliminate the interference of urease activity in the oral cavity before the [C-13]-urea breath test (UBT). However, the effectiveness of mouth washing prior to testing has not been demonstrated clearly in the literature. Thus, the present study was designed to examine the consistency of the [C-13]-UBT and the effects of mouth washing on it. Methods: A total of 101 healthy volunteers underwent the [C- 13]-UBT three times. The first and second tests used a standard protocol and collected samples at 5, 10, 15 and 30 min. In the third test, the procedure was the same except that mouth washing was omitted. Results: We used 5 permil ( parts per thousand) as the cut-off value and there were 21 ( 20.8%) positive cases. The kappa values for the samples collected at 5, 10, 15 and 30 min between the first and second tests were 0.68, 0.97, 1 and 1, respectively, and all showed good consistency, except for the sample collected at 5 min. Judging from the mean value of the [C-13] enrichment of the first and second tests (with mouth washing) and the third test ( without mouth washing), 50 (63.3%), 15 (18.8%), 0 and 0 cases at 5, 10, 15 and 30 min, respectively, changed from negative to positive. There were 14 (17.5%) and six (7 .5%) cases at 15 and 30 min, respectively, whose [C- 13] enrichment changed from less than 3 (negative) to between 3 and 5 ( border zone). Conclusions: These results indicate that mouth washing had an important effect on samples obtained at 5 and 10 min, while this influence decreased at 15 min and was lowest at 30 min. (C) 2001 Blackwell Science Asia Pty Ltd.