Are anti‑TPO (thyroid peroxidase antibody) and TRAb (TSH‑receptor antibody) the same test?

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Last updated: October 8, 2026 • View editorial policy

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No, Anti-TPO and TRAb Are NOT the Same Test

Anti-TPO (thyroid peroxidase antibody) and TRAb (TSH-receptor antibody) are completely different antibodies that target different thyroid antigens and serve distinct clinical purposes. 1, 2

Key Differences

Different Targets

  • Anti-TPO: Targets thyroid peroxidase enzyme, a protein involved in thyroid hormone synthesis
  • TRAb: Targets the TSH receptor on thyroid cells, can stimulate or block the receptor 1

Different Clinical Uses

TRAb is used to:

  • Diagnose Graves' disease with near 100% sensitivity and specificity 1
  • Predict relapse risk after antithyroid drug treatment 3
  • Assess fetal/neonatal thyroid dysfunction risk in pregnant women with Graves' disease 4, 2
  • Diagnose Graves' orbitopathy, especially in euthyroid patients 5

Anti-TPO is used to:

  • Identify autoimmune thyroiditis (Hashimoto's thyroiditis) 2
  • Predict progression from subclinical to overt hypothyroidism (4.3% per year with positive anti-TPO vs 2.6% without) 2, 6
  • Evaluate recurrent miscarriage risk 4, 2
  • Distinguish autoimmune from non-autoimmune thyroid disease 1

Diagnostic Algorithm for Thyrotoxicosis

When evaluating thyrotoxicosis with suppressed TSH:

  1. First-line: Order TRAb to diagnose Graves' disease 1

    • If TRAb positive → Graves' disease confirmed
    • If TRAb negative → Proceed to step 2

  2. Second-line: Order anti-TPO to assess for autoimmune thyroiditis 1

    • Positive anti-TPO suggests Hashimoto's thyroiditis (including hashitoxicosis)
    • Negative suggests non-autoimmune causes

Common Clinical Pitfall

Do not assume all thyroid antibodies are interchangeable. In Graves' disease, approximately 75% of patients have elevated anti-TPO, but TRAb is the diagnostic antibody 2. Conversely, in Hashimoto's thyroiditis, anti-TPO is typically positive (86% sensitivity) while TRAb is usually negative 7. Testing the wrong antibody can lead to misdiagnosis.

Antibody Patterns by Disease

  • Graves' disease: TRAb positive (83-96%), anti-TPO often positive (75%) 7, 8
  • Hashimoto's thyroiditis: Anti-TPO positive (86%), TRAb typically negative (13%) 7
  • Hashitoxicosis: Anti-TPO positive, TRAb negative, transient hyperthyroidism 9

The guideline evidence clearly establishes these as separate tests with distinct clinical roles that cannot substitute for one another 1, 2, 5.

References

1
Guideline

diagnostic procedure in suspected graves' disease.

Annales d'endocrinologie, 2018

2
Guideline

clinical practice guidelines for hypothyroidism in adults: cosponsored by the american association of clinical endocrinologists and the american thyroid association.

Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologist, 2012

5
Research

Thyroid autoantibodies.

Journal of clinical pathology, 2023

9
Guideline

graves' disease in children.

Annales d'endocrinologie, 2018

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