Performance characteristics of scintigraphic transit measurements for studies of experimental therapies

Background: The intra- and inter-individual reproducibility of gastrointestinal and colonic transit tests require full characterization. Aims: (i) To characterize the normal values and reproducibility effects of age and gender on the scintigraphic transit of solids in health. (ii) To compare scintigraphic and radio-opaque marker measurements of colonic transit. (iii) To estimate demonstrable effect sizes for different transit end-points based on observed variations. Methods: A scintigraphic gastrointestinal and colonic transit study and the mean colonic transit time were measured using radio-opaque markers in 37 healthy volunteers; 21 subjects had a repeat scintigraphic test 3 weeks later. Results: Gastric emptying at 4 h was highly reproducible (coefficient of variation, 4%) on repeat testing. The colonic measurement varied by more than 1 geometric centre unit in 37% of subjects at 24 h and in 26% of subjects at 48 h. There were no age- or gender-related differences in transit. Effect sizes demonstrable with 14 subjects per group were in the range previously shown to be clinically relevant: 25% change in gastric emptying at 4 h; 1.5 geometric centre unit change in colonic transit at 48 h. Conclusions: These data demonstrate the reproducibility and performance to be expected of transit measurements and are essential for designing studies in experimental therapeutics.