[Detection of thyroid hormone antibodies using a radial immunodiffusion method]

T3 and T4 autoantibodies just as protein binding anomalies are the cause of discrepancies of thyroid hormone assays as against actual thyroid function. Depending on the separation techniques used, autoantibodies lead to false low or high T3 or T4 values. A series of 105 preselected thyroid patients was investigated as to the presence of T3 and T4 autoantibodies. Only in one of these patients T3 autoantibodies could be documented as cause for elevated fT3 values in otherwise euthyroid function (clinically euthyroid, positive TRH/TSH response, euthyroid peripheral tissue parameters). The remaining 104 subjects showed neither T4 nor T3 autoantibodies. The method of investigation developed for final diagnosis of T4 and T3 autoantibodies was done by a radial immune diffusion technique. Here the serum sample was incubated for 12 hours at room temperature with radioactive labelled T3 or T4, then applied on to an antiIgG immune diffusion disc. The radioactivity of the punched precipitation area is measured. This method is quick and easily carried out and highly suitable as screening method.