Anti-thyroid peroxidase antibodies in thyroid disorders and non-thyroid autoimmune diseases

A new commercial method for measurement of anti-thyroid peroxidase (anti-TPO DYNOtest, Henning, Berlin) was evaluated in normal subjects and in patients with autoimmune thyroid and non-thyroid diseases, and compared to an immune fluorescence method for measurement of anti-microsomal antibodies (MicAb), and a radioimmunological method for quantifying thyroglobulin antibodies (TgAb). The majority of normal subjects had anti-TPO levels below 52 U/ml and patients with Hashimoto's thyroiditis had levels above 200 U/ml, with a good correlation to MicAb. In other autoimmune thyroid diseases the correlation was less pronounced. In non-thyroid autoimmune diseases MicAb showed falsely positive reactions in the presence of other autoantibodies, e.g. mitochondrial antibodies. The present study indicates that the anti-TPO method should probably replace measurements of MicAb for routine clinical use, thus providing a sensitive, precise, antigen specific method with the ability to reveal quantitative fluctuations. The study also indicates that TgAb could be abolished in routine diagnosis of autoimmune thyroid diseases and be reserved for special clinical situations, research purposes as well as measurement in sera before evaluation of serum thyroglobulin levels.