The Wagner-Nelson method makes the [13C]-breath test comparable to radioscintigraphy in measuring gastric emptying of a solid/liquid mixed meal in humans

1. Scintigraphy is the gold standard for measuring gastric emptying, but the use of radioactive isotopes can produce substantial irradiation. The [C-13]-acetate/octanoic acid breath test is widely used as a non-radioactive alternative. 2. The half [(CO2)-C-13] excretion time (T-1/2b) is closely correlated with the scintigraphic half-emptying time (T-1/2s). However, T-1/2b is consistently remote from T(1/2)s, because the distribution of [(CO2)-C-13] into the bicarbonate pool delays the respiratory excretion of the [C-13] marker, which has already been emptied from the stomach. The time for the distribution process should be adjusted to diminish the discrepancy between the results of the scintigraphic and breath tests. 3. The Wagner-Nelson method provides an accurate profile of drug absorption. We have recently applied the Wagner-Nelson method to breath testing to adjust the time for [(CO2)-C-13] distribution. In the present study, the [C-13]-breath test with Wagner-Nelson analysis was compared with scintigraphy. 4. Six female volunteers simultaneously underwent scintigraphy and the breath test on two occasions, either to measure gastric emptying of the liquid phase (16 kcal) or for that of the solid phase (214 kcal). Time-percentage gastric retention curves were generated by scintigraphy and the breath test with Wagner-Nelson analysis. The half-emptying times were determined by interpolation from the scintigraphic curve (T-1/2s) and the Wagner-Nelson curve (T-1/2WN). T-1/2b was calculated by conventional curve-fitting techniques. 5. For liquid and solid emptying, the gastric retention curves generated by the Wagner-Nelson method were comparable to the scintigraphic retention curves. For the liquid, T-1/2b was significantly longer than T(1/2)s (93.8 +/- 7.3 vs 14.2 +/- 9.3 min, respectively; P < 0.0001), as was also observed for the solid phase (147.8 +/- 34.4 vs 35.3 +/- 11.2 min, respectively; P < 0.0001). In contrast, no significant differences were found between T-1/2WN and T-1/2s for the liquid (13.5 +/- 5.0 vs 14.2 +/- 9.3 min, respectively; P = 0.734) and the solid (45.8 +/- 10.2 vs 35.3 +/- 11.2 min, respectively; P = 0.051) phase. 6. In conclusion, Wagner-Nelson analysis makes the [C-13]breath test comparable to scintigraphy.