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Test Name:
Thyroid Peroxidase Antibodies
- SBMF No:
30019 - Performance Lab Name:
Manual Lab - Test Mnemonic:
TPO- - ABN:
Not required - CPT Code:
86376 - LOINC Code:
8099-4 - Also Known As:
Anti-Microsomal Antibodies
Anti-Thyroid Peroxidase Antibodies
Anti-Thyroperoxidase Antibodies
Anti-TPO Antibodies
Hashimoto Disease
Microsomal Antibodies
Thyroperoxidase Ab, Serum
TPO Antibodies - Also See:
30020 Thyroglobulin Antibodies
30022 Thyroglobulin with Thyroglobulin Antibodies - Spec Type:
Serum - Spec Container:
Gold top (SST) or red top (serum) tube - Pref Vol:
1.0 mL - Min Vol:
0.3 mL - Fasting:
No - Spec Collect:
Routine venipuncture - Spec Process:
Clot 30 minutes
Promptly centrifuge 15 minutes
Immediately transfer serum to separate plastic tube - Spec Store Transport:
Refrigerated - Spec Stability:
1 week refrigerated (2-8°C)
6 months frozen (-20°C) – Do not use frost-free units that undergo repeated freeze/thaw cycles - Spec Reject:
Severely hemolyzed, lipemic, or icteric sample - Methodology:
Chemiluminescent Immunoassay (CLIA) - Use:
Primarily used to diagnose autoimmune thyroiditis - Clinical Significance:
Thyroid peroxidase is a 107,000 MW membrane-bound glycoprotein with a heme prosthetic group that catalyzes the iodide oxidation of tyrosine residues on thyroglobulin in the synthesis of the iodothyronines T3 and T4. Thyroid perioxidase is now generally recognized as the principal autoantibody protein in thyroid microsomes and until recently was known as thyroid antimicrosomal antigen. The nucleotide sequence for human thyroid peroxidase cDNA has been reported to code for a protein of 933 amino acids. The protein has hydrophobic domains at the amino and carboxy termini, which are consistent with it being a membrane associated protein. Titers of microsomal antibodies and TPO antibodies in sera have correlated very well in patients with autoimmune thyroid disease.
A genetically engineered soluble form of TPO containing the extracellular region of TPO but lacking the transmembrane and intra-cytosplasmic regions has been developed and provides an easily reproducible source of purified protein for use in the diagnostic detection of TPO autoantibodies. This recombinant TPO has been demonstrated to recognize TPO autoantibodies in patients to the same extent as full-length membrane associated TPO. Autoimmune thyroid disease B cell epitopes on human TPO have been shown to be directed to the amino acid regions between 456 and 845 (up to the junction of the plasma membrane) on the 933 amino acid protein.
The autoantibodies to human TPO are heterogeneous. The proportions of subclasses (IgG 1-4, IgM) are different from patient to patient as are their affinities. The majority of TPO autoantibodies, as with all antibodies, have been found to be directed against non-linear discontinuous conformational epitopes, although there are linear epitopes. Autoantibodies to TPO also have been demonstrated to inhibit enzymatic activity and cross-react with other peroxidases. Thyroid peroxidase autoantibodies are of pathological importance because they are present in the majority of Hashimoto’s thyroiditis patients and correlate with the active phase of the disease. Unlike thyroglobulin autoantibodies, they may damage thyroid cells by complement fixation.
- Reference Range:
0.0-35.0 IU/mL - Additional Test Info:
As many as 15% of euthyroid patients may present with elevated levels of thyroid autoantibodies.
Interference from Rheumatoid Factor as well as anti-TSH, anti-T3 and anti-T4 autoantibodies may occur. - Day Run:
Mon, Wed, Fri - Time Run:
8:00 am - Time Reported:
3:30 pm - Test Type:
IMMUNOLOGY
