Validation of the lactose-[C-13]ureide breath test for determination of orocecal transit time by scintigraphy

The breath test using oral administration of a C-13-labeled substrate, lact ose-ureide (LU), to measure orocecal transit time (OCTT) was validated agai nst Tc-99m-scintigraphy. Although LU is not absorbed in the human small int estine, colonic bacteria readily metabolize LU, producing C-13-labeled CO2. The time at which (CO2)-C-13 appears in breath corresponds to the OCTT. Me thods: Twenty-two healthy volunteers ingested a meal labeled with Tc-99m an d C-13-LU. Scintigraphy was performed over 8 h at time intervals of 10 or 1 5 min. OCTT with scintigraphy was defined as the time at which at least 10% of the label had entered the colon. Breath samples were obtained every 10- 15 min for 10 h and measured by isotope ratio mass spectrometry. OGTT was d efined as the time of first significant increase above baseline. The result s were compared using correlation and Altman-Bland statistics. Results: OCT T results from scintigraphy (mean OGTT = 283 +/- 53 min) and breath test (m ean OCTT = 292 +/- 58 min) correlated well (r = 0.94). Altman-Bland statist ics showed close agreement between scintigraphy and breath test. No signifi cant difference between male and female subjects was observed. Conclusion: The breath test using C-13-LU is a valid alternative to scintigraphy techni ques for measuring OGTT.