Thyroid Binding Immunoglobulin testing is used for autoimmune thyroid disease, including:
- Differential diagnosis of aetiology of thyrotoxicosis in patients with ambiguous clinical signs and/or contraindicated (e.g. pregnant or breast-feeding).
- Diagnosis of clinically suspected Grave’s disease but normal thyroid function tests.
- Determining the risk of neonatal thyrotoxicosis in a foetus of a pregnant female with active or past Graves disease.
- Differential diagnosis of gestational thyrotoxicosis versus first trimester manifestation or recurrence of Graveâ€™s disease.
- Assessing the risk of Graves disease relapse after anti-thyroid drug treatment.
Autoimmune thyroid disease is characterized by the presence of auto antibodies against various thyroid components, namely the thyrotropin receptor (thyroid-stimulating hormone receptor [TSHR]), thyroid-peroxidase (TPO), and thyroglobulin (Tg), as well as an inflammatory cellular infiltrate of variable severity within the gland. Among the auto antibodies found in autoimmune thyroid disease, TSHR auto antibodies are most closely associated with disease pathogenesis. All forms of autoimmune thyrotoxicosis (Graves disease, Hashitoxicosis, neonatal thyrotoxicosis) are caused by the production of TSHR-stimulating auto antibodies. The role of the TPO and Tg auto antibodies in either autoimmune thyrotoxicosis or autoimmune hypothyroidism is less well established; they may merely represent epiphenomena. Detectable concentrations of anti-TPO antibodies are observed in most patients with autoimmune thyroid disease (e.g Hashimoto’s thyroiditis, idiopathic myxedema, and Graves disease).
|1.0 – 1.5 U/L Borderline||A TBII of 1.5U/L equates to 20% inhibition|
|>1.5 U/L Positive||3.0 U/L equates to 40% inhibition|
|4.0 U/L equates to 50% inhibition|
Serum sample required (SST). Plasma samples are unacceptable.
Both inhibitory and stimulatory antibodies are measured. If positive, results usually assumed to be stimulatory abs, particularly if biochemical, clinical signs of hyperthyroidism.