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

To validate a ¹³C-Spirulina platensis breath test for measurement of accelerated or delayed gastric emptying, we measured gastric emptying of egg containing ¹³C-S. platensis and ^99mTc-sulphur colloid by breath ¹³CO₂ 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 ¹³CO₂ (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 > l50 min. Breath test detected abnormal emptying with a sensitivity of 86% and specificity of 80%. Thus, the ¹³C-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.