A radioimmunoassay for the detection of adrenal autoantibodies

A solid phase radioimmunoassay for adrenal antibodies is described. In the assay plastic tubes coated with adrenal microsomes (100 micrograms/ml) were incubated with human sera diluted from 1:50 to 1:5000 and the retained antibodies detected by subsequent incubation with 125I-labelled protein A. The method was precise over the range of serum dilution of 1:250 to 1:5000. In the group of 30 patients with Addison's disease 19 had positive results in adrenal antibody radioimmunoassay (RIA). Comparative studies of RIA and immunofluorescence (IFL) revealed that there was partial correlation of adrenal antibody results in patients with high titre antibodies whereas RIA usually was more sensitive than IFL in patients with low titre antibodies. Computerized tomography (CT) displayed bilateral adrenal atrophy in most patients who had adrenal antibodies. On the other hand, patients with low RIA results and negative IFL antibodies had predominantly adrenal calcifications on scans.