Postheparin plasma diamine oxidase in patients with small bowel Crohn's disease.

Diamine oxidase (DAO) is an enzyme located almost exclusively in villus tip enterocytes of mammals. Its plasma activity, normally very low, is enhanced by intravenous heparin, which releases the enyzme from small bowel enterocytes into the blood. Plasma postheparin DAO (PHD) values have been shown to be significantly reduced in patients with malabsorption and villous atrophy and inversely correlated with 24-h fecal fat, thus suggesting that PHD reflects the mature enterocytic mass. We have assayed PHD in 51 patients with small bowel Crohn's disease by measuring the area under the plasma DAO curve over a 120-min period after an intravenous bolus of 15,000 IU of heparin. Postheparin plasma DAO was significantly lower (p less than 0.001) in patients (328 +/- 175 U/ml.min) than in 20 normal subjects (508 +/- 101 U/ml.min; range, 391-749). Postheparin diamine oxidase values were inversely correlated with Crohn's disease activity index (CDAI), but no correlation was found with extent of disease assessed radiologically by either double-contrast small bowel enema or barium meal follow-through. In 6 patients with active disease (CDAI, 297 +/- 99) and low PHD values (188 +/- 100 U/ml.min), the assay was repeated after a clinically effective course of antiinflammatory drugs. A significant increase in PHD values (388 +/- 112 U/ml.min) was observed (p less than 0.005). These data indicate that mucosal involvement is common in small bowel Crohn's disease and that PHD may be useful in assessing and monitoring mucosal damage in these patients.