Autoimmune thyroid gland disorders are characterized by detection of anti-thyroid antibodies, primarily against thyroglobulin and/or microsomal thyroid antigens. Recently it has been shown that thyroid peroxidase (TPO) is the protein responsible for microsomal antigenicity1. In addition to chronic thyroiditis, thyroid autoantibodies may be found in other thyroid disorders. These autoantibodies may also occur in apparently normal subjects. Thyroid microsomal (TPO) autoantibodies occur in sera of most autoimmune thyroid disease patients and predict raised serum TSH levels in random populations. The presence of autoantibody does not imply active tissue destruction. Microsomal (TPO) antibody level correlates with the degree of lymphoid infiltration of the thyroid gland. Thyroid autoantibodies are detected by a variety of immunoassays. Two common methods are indirect hemagglutination (IHA) and indirect fluorescent antibody (IFA) techniques. ImmunoDOT Thyroid Autoimmunity Test uses highly purified human thyroglobulin devoid of microsomal antigen and recombinant human thyroid peroxidase (microsomal antigen) which does not contain contaminating thyroglobulin and/or mitochondria found in other microsome antigen preparations. These purified antigens are used in a dipstick format enzyme immunoassay technique.