[1st direct comparison of allergic side effects of dextran with and without hapten].

In a Swiss multicentre study for evaluation of heparindihydroergotamine in the prevention of postoperative thromboembolic complications, 3887 patients received dextran 70 for comparison. During this trial monovalent hapten-dextran was introduced in two of the participating centres for clinical evaluation. 701 patients in the trial therefore received either 10 or 20 ml hapten before the first dextran infusion was started. Thus, direct evaluation of the incidence of dextran-induced anaphylactoid reactions in two groups of patients, on receiving hapten prevention and the other not, was possible for the first time. 32 dextran-induced anaphylactoid reactions occurred in the 3186 patients not receiving hapten. The incidence of these reactions is therefore 1%. Four of the reactions were severe and 1 was fatal. In the group of patients receiving hapten there was no reaction either to the dextran infusion or to the hapten injection. According to the zero hypothesis, 7 dextran-induced anaphylactoid reactions were expected.