Postheparin plasma diamine oxidase in subjects with small bowel mucosal atrophy

Diamine oxidase (DAO) is an enzyme whose low plasma values are enhanced by an intravenous injection of heparin, which releases the enzyme from the enterocytes of the villous tips. In 20 normal controls and 15 untreated subjects affected with an overt malabsorption syndrome and subtotal atrophy shown by Crosby jejunal mucosa biopsy (12 suspected celiac disease and three small bowel lymphoma), plasma diamine oxidase was assayed, over 2 hr following an intravenous bolus of 15,000 IU heparin. Plasma postheparin DAO concentrations and the corresponding values of the area under curve, expressed as units/ml·min (mean±sd), were significantly lower in the patients (celiac sprue: 138±62; lymphoma: 83±42) compared to normals (481±104). DAO area values were well correlated (r=0.81;P<0.001) with 24-hr fecal fat excretion but not with xylosuria. Our data suggest that postheparin plasma DAO assay may be useful to detect and quantitate small bowel mucosal atrophy in patients with malabsorption syndromes.