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.