Utility of a 13C-Spirulina Stable Isotope Gastric Emptying Breath Test in Diabetes Mellitus.

Background: The carbon-13 spirulina gastric emptying breath test (GEBT) is approved to identify delayed, but not accelerated, gastric emptying (GE). We compared the utility of the GEBT to scintigraphy for diagnosing abnormal GE in patients with diabetes mellitus.

Methods: Twenty-eight patients with diabetes ate a 230-kcal test meal labeled with technetium 99 m and ¹³C-spirulina, after which 10 scintigraphic images and breath samples (baseline, 15, 30, 45, 60, 90, 120, 150, 180, 210, and 240 min) were collected on 2 occasions 1 week apart. We assessed the accuracy of ¹³C-spirulina GEBT excretion rate (percent dose multiplied by 1000 [kPCD] min^-1) values to predict scintigraphic half-life and distinguish between normal, delayed, and accelerated GE and the intraindividual reproducibility of the GEBT.

Key results: Scintigraphy revealed normal, delayed, and accelerated GE, respectively, in 17 (30%), 29 (52%), and 10 (18%) test results. GE T½ values measured with scintigraphy and GEBT were highly concordant within individuals; the intraindividual reproducibility was 34% (scintigraphy) and 15% (GEBT). Compared to current criteria, the kPCD150 (150 min) and kPCD180 values provided equally sensitive (90%) and more specific (81% vs. 67%) approach for distinguishing between delayed versus normal/accelerated GE. A new metric (kPCD60-kPCD15 min) was 90% sensitive and 83% specific for distinguishing between accelerated versus normal/delayed GE. These findings were used to create nomograms and an algorithm for interpreting GEBT results.

Conclusions and inferences: Among patients with poorly controlled diabetes, the ¹³C-spirulina GEBT can accurately and precisely assess GE and effectively distinguish between normal, delayed, and accelerated GE.