Cellobiose/mannitol test: physiological properties of probe molecules and influence of extraneous factors.

The influence of gastric emptying, intestinal transit, renal and hepatic function, and variations in the timing of urine collections, on the cellobiose/mannitol test of intestinal permeability has been studied. None of these extraneous factors influences the cellobiose/mannitol recovery ratio, and there is only a modest effect of renal function on urinary mannitol recovery. Cellobiose is almost totally recovered in the urine within 10 h of intravenous injection, whilst mannitol is less completely recovered, perhaps due to hepatic metabolism. The simultaneous administration of two probe molecules in the cellobiose/mannitol test, and the use of a ratio to express results, thus achieves the desired object of minimising the effect of extraneous factors on the test result. The cellobiose/mannitol test is therefore not subject to the limitations of previous tests of intestinal permeability using orally administered probe molecules, and is widely applicable as a screening test for coeliac disease.