111Indium-transferrin for localization and quantification of gastrointestinal protein loss.

Objective. To evaluate the indium-111 (111In)-transferrin method as a means of localization and quantification of gastrointestinal protein loss. Methods. Fourteen patients and 15 healthy subjects underwent an 111In-transferrin study consisting of abdominal scintigraphy, whole-body counting measurement and determination of plasma activity of 111In during the course of 5 days. Two of the patients went through a subsequent chromium-51-trichloride test with analysis of radioactivity in faeces in order to compare the results of the two methods. Results. The patients had a mean±SEM whole-body loss of 111In of 10.9±2.9% for 96 h, while the healthy controls lost 1.8±1.3% (p=0.0045). The decay in plasma activity followed biexponential kinetics. The characteristic plasma transit time was 5.0±1.0 h in patients and 12.1±1.5 h in controls (p=0.0007). Scintigraphically, patients had obvious abdominal foci of activity, while the control subjects showed diffuse activity. Anatomic localization of the leaking spot seemed more uncertain. By comparison with the 51Cr trichloride test, the loss of radio-labelled protein appeared to be in the same order of magnitude. Conclusions. Quantification of gastrointestinal protein loss can be done without collecting faeces. Normal subjects have a loss of a few per cent, making the 111In-transferrin method comparable with the former standard using 51CrCl3-trichloride. Plasma measurements of 111In are not predictive of the magnitude of the loss. Scintigraphic localization of the site of the loss needs to be optimized, for instance by serial imaging or image fusion with an anatomical modality. [ABSTRACT FROM AUTHOR]