Validation of a stable isotope gastric emptying test for normal, accelerated or delayed gastric emptying

To validate a C-13-Spirulina platensis breath test for measurement of accelerated or delayed gastric emptying, we measured gastric emptying of egg containing C-13-S. platensis and Tc-99m-sulphur colloid by breath (CO2)-C-13 every 15 min over 3 h and scintigraphy every 15-30 min over 5 h in 57 healthy volunteers. Thirty-three received no treatment, 10 received erythromycin, and 14 atropine. A generalized linear regression model predicted half-emptying time by scintigraphy (t(1/2S)) from breath (CO2)-C-13 (t(1/2B)) data. Accuracy was assessed by standard deviation (SD) of differences between t(1/2S) and t(1/2B) and by receiver operating characteristic (ROC) curves. Regression models using breath samples at baseline, and 45, 90, 105 and 120 min, predicted t(1/2B) (mean +/- SD) at 118 +/- 59 min, similar to t(1/2S) (118 +/- 67 min). Correlation between t(1/2B) and t(1/2S) was significant (r = 0.88; P < 0.0001). Differences between t(1/2S) and t(1/2B) were: 18-19.2 min for t(1/2) < 70-150 min, and 68.3 min for t(1/2) > 150 min. Breath test detected abnormal emptying with a sensitivity of 86% and specificity of 80%. Thus, the C-13-S. platensis test measures gastric emptying t(1/2) for solids, which is accelerated or delayed to mimic a range of conditions from dumping syndrome to severe gastroparesis, with high sensitivity and specificity. Additional breath samples are needed to increase sensitivity in detecting accelerated gastric emptying.