Plasma postheparin diamine oxidase activity. Development of a simple technique of assessing Crohn's disease.

Plasma diamine oxidase (DAO) activity may reflect intestinal involvement in Crohn's disease. The purpose of this study was to develop a simple heparin stimulation test for assessing postheparin plasma diamine oxidase activity in Crohn's disease. Ten volunteers and five patients with Crohn's disease received 1000 units and 3000 units of heparin intravenously and plasma samples were obtained at timed intervals. Plasma DAO activity increased significantly, compared with basal values, 30 minutes after 3000 units of heparin in both volunteers (26.2 +/- 5.0 vs. 4.5 +/- 0.5 units/ml) and patients with Crohn's disease (14.6 +/- 2.0 vs. 4.0 +/- 1.1 units/ml, P less than .05) and was significantly greater in the volunteers. There was no significant increase in DAO activity after 1000 units of heparin. Plasma DAO activity increased significantly within 15 minutes after 3000 units of heparin and remained at this high level at 60 minutes. Postheparin DAO activity correlated with the integrated area under the DAO activity curve. Plasma DAO activity correlated with the Crohn's Disease Activity Index in the patients with Crohn's disease. Plasma DAO activity, 30 minutes after the intravenous administration of 3000 units of heparin, should reflect intestinal involvement in Crohn's disease.