Application of isotope-selective nondispersive infrared spectrometry (IRIS) for evaluation of [13C]octanoic acid gastric-emptying breath tests: comparison with isotope ratio-mass spectrometry (IRMS).

Suitability of isotope-selective nondispersive infrared spectrometry (IRIS) for evaluation of [13C]octanoic acid gastric-emptying breath test was assessed and compared with standard isotope ratio-mass spectrometry (IRMS). The estimated bias of IRMS and IRIS measurements of baseline-corrected 13CO2 exhalation amounted to +/-0.1 and +/-0.6 delta 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 13CO2 exhalation: half-emptying time (t1/2,breath, 90 +/- 39 min), lag phase (tlag,breath, 34 +/- 27 min), and gastric emptying coefficient (GEC, 2.9 +/- 0.5). A reasonable linear correlation was found between the two methods (y = IRIS, x = IRMS) with respect to delta delta values (y = 0.35 + 0.92x, r = 0.985, Sy[symbol: see text]x = +/-0.6, n = 1116) and a rather good agreement of the computed gastric emptying parameters was obtained (t1/2,breath: y = 0.99x + 4.06, Sy[symbol: see text]x = +/- 6.3; tlag, breath: y = 0.97x + 0.96, Sy[symbol: see text]x = +/-3.4; GEC: y = 0.97x - 0.01, Sy[symbol: see text]x = +/-0.09).