Validation in an animal model of the carbon 13-labeled mixed triglyceride breath test for the detection of intestinal fat malabsorption

Objective: To determine, in a rat model of fat malabsorption, the potency o f the carbon 13-labeled mixed triglyceride (C-13-MTG) breath test as a noni nvasive, patient-friendly replacement for classic fat balance studies, Study design: Comparison of the percentage of Fat absorption, detected by f at balance, with the (CO2)-C-13 recovery of the C-13-MTG breath test in rat s fed high-fat chow and varying amounts of the lipase inhibitor, orlistat ( 0, 50, 200, and 800 mg per kilogram of chow), for 5 days. Results: On orlistat administration, total fat absorption decreased from 80 .2% +/- 2.2% to 32.8% +/- 3.7% (mean +/- SEM, 0 mg and 800 mg of orlistat p er kilogram. of chow, respectively; P < .001). Correspondingly, breath (CO2 )-C-13 recovery from C-13-MTG at 6 hours decreased from 84.5% +/- 7.8% to 4 2.0% +/- 1.5% of the dose (0 mg and 800 mg of orlistat per kilogram of chow , respectively; P < .001). The 6-hour recovery of breath (CO2)-C-13 appeare d to be highly correlated with the percentage of fat absorption (r = 0.88, P < .001). In rats with fat absorption higher than 70%, however, the coeffi cient of variation of the C-13-MTG breath test was 3-fold larger than that of the fat balance. Conclusions: The C-13-MTG breath test could potentially replace the fat bal ance method for comparing fat absorption efficacy between groups. Yet, a co nsiderable interindividual variation of the C-13-MTG breath test under cond itions of relatively mild fat malabsorption does not support its applicatio n for diagnostic purposes in individuals.