Increased in vitro histamine release by radiographic contrast media in patients with history of incompatibility.

This study was designed to compare in vitro leucocyte histamine release in patients with a history of previous radiographic contrast media (RCM) reactions and normal controls. Peripheral leucocytes of ten patients with a positive history of RCM imcompatibility and nineteen normal volunteers were stimulated in vitro with different RCM in different concentrations and the amount of histamine released was measured in the supernatant. There was a significant increase in histamine release induced by RCM in low doses (0.02-0.1 M) in the patients as compared to the normals. At the high doses (0.2-0.3 M), no significant differences were found. Leucocytes from four of the patients were stimulated preferentially by the dye responsible for the incompatibility. Six patients showed no such preference. The increased "releasability" of the patients' leucocytes could not be transferred by serum. Normal leucocytes, when incubated with serum from "high releasing" patients did not show increased histamine release after stimulation with the respective dye. It is suggested that an excessive non-immunological response of basophil leucocytes to RCM stimulation might, in part, account for the adverse clinical reactions observed. Furthermore, leucocyte histamine release might be a useful diagnostic tool for detecting patients with a high risk of developing contrast media reactions.