APPLICATION OF ISOTOPE-SELECTIVE NONDISPERSIVE INFRARED SPECTROMETRY (IRIS) FOR EVALUATION OF [C-13]OCTANOIC ACID GASTRIC-EMPTYING BREATH TESTS - COMPARISON WITH ISOTOPE RATIO MASS-SPECTROMETRY (IRMS)

Suitability of isotope-selective nondispersive infrared spectrometry ( IRIS) for evaluation of [C-13]octanoic acid gastric-emptying breath te st was assessed and compared with standard isotope ratio-mass spectrom etry (IRMS). The estimated bias of IRMS and IRIS measurements of basel ine-corrected (CO2)-C-13 exhalation amounted to +/- 0.1 and +/- 0.6 De lta delta values (n = 360), respectively. In breath tests performed on 60 diabetic patients, the gastric emptying parameters were calculated by nonlinear regression analysis of the time course of (CO2)-C-13 exh alation: half-emptying time (t(1/2,breath), 90 +/- 39 min), lag phase (t(lag,breath), 34 +/- 27 min), and gastric emptying coefficient (GEC, 2.9 +/- 0.5). A reasonable linear correlation was found between the t wo methods (y = IRIS, x = IRMS) with respect to Delta delta values (y = 0.35 + 0.92x, r = 0.985, S-y\x = +/-0.6, n = 1116) and a rather good agreement of the computed gastric emptying parameters was obtained (t (1/2,breath): y = 0.99x + 4.06, S-y\x = +/-6.3; t(lag,breath): y = 0.9 7x + 0.96, S-y\x = +/-3.4; GEC: y = 0.97x - 0.01, S-y\x = +/-0.09).