The autologous serum skin test: a screening test for autoantibodies in chronic idiopathic urticaria

One‐third of patients with chronic idiopathic urticaria (CIU) have circulating functional autoantibodies against the high affinity IgE receptor FcεRI, or IgE. The intradermal injection of autologous serum causes a weal and flare reaction in many patients with CIU, and this reaction forms the basis of the autologous serum skin test (ASST). We have determined the parameters of the ASST which define the optimal sensitivity and specificity for the identification of patients with autoantibodies. Two physicians (R.A.S. and C.E.H.G.) performed ASSTs in a total of 155 patients with CIU, 40 healthy control subjects, 15 patients with dermographism, nine with cholinergic urticaria and 10 with atopic eczema. Patients were classified as having functional autoantibodies by demonstrating in vitro serum‐evoked histamine release from the basophils of two healthy donors. There were significant differences (P