Accuracy of the whole body retention half-life of 75SeHCAT in the diagnosis of ileal dysfunction in patients with Crohn's disease.

The measurement of the whole body retention of the synthetic taurine conjugated trihydroxy bile acid 75SeHCAT has been suggested as a new clinical test for the function of the terminal ileum. Because of the frequent occurrence of ileal dysfunction in Crohn's disease (CD), the accuracy of the SeHCAT test was studied in 64 patients with CD in various clinical conditions. A positive test result (retention half-life less than 1.2 days) was seen in 48.4% of the patients with ileal involvement (true positive tests) whereas a negative test was seen in 33 of the 64 patients. In 21 of the 33 patients (63.6%) the test was false negative since ileal inflammation or resection was confirmed by radiology or endoscopy. In 14 of those 21 patients with false negative test results a stenosis of the intestinal lumen was diagnosed. At a specificity of 100% the sensitivity of the SeHCAT test was 59.6% and the efficiency was 67.2%. If patients with known stenosis were excluded sensitivity improved to 79.4%. In conclusion, calculation of the whole body retention half-life of SeHCAT does not seem to be a valuable screening test for the diagnosis of ileal dysfunction. In CD, a pathologic test result identifies ileal dysfunction with high accuracy.