Performance characteristics of scintigraphic transit measurements for studies of experimental therapies

The intra- and inter-individual reproducibility of gastrointestinal and colonic transit tests require full characterization.

(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.

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.

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.

These data demonstrate the reproducibility and performance to be expected of transit measurements and are essential for designing studies in experimental therapeutics.