Scrutiny of 13C-phenylalanine breath test reproducibility

ABSTRACTWe evaluated the reproducibility of the 13C-phenylalanine breath test (13C-PheBT). On three separate days, 21 healthy volunteers (11 F and 10 M) underwent 13C-PheBT with 100 mg l-[1-13C]phenylalanine taken orally. Short-term reproducibility was evaluated with paired examinations taken 3 days apart; paired examinations separated by 23 days (median) served for the medium-term reproducibility assessment. Expiratory air was sampled at 19 points throughout 3 h. Determined limited reproducibility of the 13C-PheBT must be taken into consideration while interpreting the results of this diagnostic tool. The results of this study imply the following conclusions: (i) From among the three parameters examined, the cumulative 13C recovery area under the curve (AUC) offers much better reproducibility than the maximum momentary 13C recovery in the expiratory air (Dmax) or the time to reach the maximum momentary 13C recovery (Tmax) (ii) Collection of the breath air samples for 2 h results in a much better reproduc...