Determination of TPO antibody levels is the most sensitive test for detecting autoimmune thyroid disease like Hashimoto thyroiditis (90%), Idiopathic myxedema and Graves disease (60-80%). Presence of TPO antibodies in subclinical hypothyroidism is associated with an increased risk of developing overt hypothyroidism. This assay helps in the diagnosis of thyroid autoimmune disorders and serves as a diagnostic tool in deciding therapy for subclinical hypothyroidism.