Clinical inquiries: How useful are autoantibodies in diagnosing thyroid disorders?

They're useful in diagnosing Graves' disease and, to a lesser extent, autoimmune thyroid disease; they can also help predict hypothyroidism. Thyrotropin receptor antibodies (TRAb) may be mildly elevated in a variety of thyroid disorders, but a TRAb level >10 U/L increases the probability of Graves' disease by a moderate to large degree (strength of recommendation [SOR]: cross-sectional study). A positive or negative thyroid peroxidase antibody (TPOAb) test increases or decreases the probability of autoimmune thyroid disease by only a small to moderate degree (SOR: 3 cross-sectional studies). Thyroid-stimulating hormone (TSH) levels >2 mU/L, although still in the normal range, can be followed up with TPOAb testing to determine whether the patient has an increased probability of developing hypothyroidism (SOR: cohort study with a vague hypothyroidism reference standard).