Reagent, Access, TPO Antibody (REF)

The Access TPO Antibody assay is a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of thyroperoxidase antibody (TPOAb) levels in human serum and plasma using the Access Immunoassay Systems.

SUMMARY AND EXPLANATION
The detection of TPOAb is an aid in the diagnosis of thyroid autoimmune disorders and enables the physician to differentiate thyroid autoimmune disorders from non-autoimmune goiter or hypothyroidism. 1,2,3,4 Disorders of the thyroid gland are frequently caused by autoimmune mechanisms with the production of autoantibodies. Thyroperoxidase (TPO) is a membrane-associated hemoglycoprotein expressed only in thyrocytes. 5 This enzyme catalyzes the oxidation of iodide on tyrosine residues in thyroglobulin for the synthesis of T3 and T4 and is one of the most important thyroid gland antigens. 6 The determination of TPOAb levels is the most sensitive test for detecting autoimmune thyroid disease. 7 The highest TPOAb levels are observed in patients suffering from Hashimoto’s thyroiditis. In this disease, the prevalence of TPOAb is about 90% of cases confirming the autoimmune origin of the disease. 2 These autoantibodies also frequently occur (60-80%) in the course of Graves’ disease. There is a good association between the presence of autoantibodies against TPO and histological thyroiditis. However, in view of the extensive regenerative capacity of the thyroid under the influence of TSH, chronic thyroid disease may be present for years before the clinical manifestation of hypothyroidism becomes evident, if ever. 8,9

METHODOLOGY
The Access TPO Antibody assay is a sequential two-step immunoenzymatic (“sandwich”) assay. A sample is added to a reaction vessel with paramagnetic particles coated with thyroperoxidase protein. The serum or plasma TPOAb binds to the thyroperoxidase. After incubation in a reaction vessel, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. The Protein A-alkaline phosphatase conjugate is added and binds to the TPOAb. After the second incubation, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. Then, the chemiluminescent substrate is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of TPOAb in the sample. The amount of analyte in the sample is determined from a stored, multi-point calibration curve.