Re-evaluation of the I-131-triolein absorption test. Analysis and purification of commercial radioiodinated triolein and clinical studies with pure preparations.

Five widely used commercial preparations of radioiodinated triolein were chromatographically analyzed for radiochemical purity. It was found that only 30 to 60 per cent of the radioactivity was in triglycerides. Remaining radioactivity was distributed among free fatty acids, their methyl esters, partially digested fats, acetoglycerides, and other substances. Fat absorption studies in 5 normal persons showed that both the purified and the commercial preparation were absorbed in considerable amounts. The absorption of purified radiotriolein was, however, less than that of the commercial preparations. In 4 patients with fat malabsorption syndrome, 3 with idiopathic steatorrhea, and 1 with terminal ileitis, the commercial preparation showed normal fat absorption whereas pure radioiodinated triglycerides were not appreciably absorbed in any of the cases. It is concluded that absorption of pure triolein is less than the I/ sup 131/-triolein absorption when the test is done with commercial preparations. This would indicate that a substantial percentage of blood radioactivity in the latter test is related to substances other than triolein. Although in 4 patients with fat malabsorption the purified radiotriolein absorption test agreed better with the clinical and the chemical fecal fat studies, its value should be determined on a larger number of patients and normalmore » controls. Chromatographic methods are described for the rapid analysis of commercial radioiodinated triolein preparations and for their purification. (auth)« less