From the Guidelines
Hashimoto's thyroiditis diagnosis is primarily based on laboratory tests that include serum TSH concentration and thyroid antibodies, such as thyroid peroxidase (TPO) antibody.
Diagnostic Tests
- Serum TSH concentration: a high TSH level is indicative of hypothyroidism, which is often associated with Hashimoto's thyroiditis 1
- Free T4: low levels of free T4, in combination with high TSH, confirm biochemical hypothyroidism 1
- Thyroid peroxidase (TPO) antibody: the presence of TPO antibodies is a specific marker for autoimmune thyroiditis, including Hashimoto's thyroiditis 1 The reference range for normal serum TSH concentration is defined as 0.45 to 4.5 mIU/L, but some investigators suggest that the upper limit of normal should be 2.5 mIU/L 1. However, in the context of diagnosing Hashimoto's thyroiditis, the focus is on the presence of high TSH and thyroid antibodies, rather than the specific cutoff value for TSH.
From the Research
Laboratory Tests for Diagnosing Hashimoto's Thyroiditis
The following laboratory tests are used to diagnose Hashimoto's thyroiditis:
- Blood tests for thyroid-stimulating hormone (TSH), free thyroxine, free triiodothyronine, thyroglobulin (Tg), thyroglobulin antibodies (Tg-Ab), thyroid peroxidase antibodies (TPO-Ab) 2
- TPO-Ab and Tg-Ab tests are used to diagnose Hashimoto's thyroiditis 2, 3, 4
- Thyroid function test (TFT) levels, ultrasonography (USG), and cytological analysis can help in early diagnosis and management of Hashimoto's thyroiditis 5
- Fine-needle aspiration cytology can be used to diagnose Hashimoto's thyroiditis 5
- Serum antibodies against thyroid antigens (thyroid peroxidase and thyroglobulin) are used to diagnose Hashimoto's thyroiditis 4
Diagnostic Criteria
The diagnosis of Hashimoto's thyroiditis relies on:
- Demonstration of circulating antibodies to thyroid antigens (mainly thyroperoxidase and thyroglobulin) 3
- Reduced echogenicity on thyroid sonogram in a patient with proper clinical features 3
- Clinical characteristics, positivity to serum antibodies against thyroid antigens, and lymphocytic infiltration on cytological examination 4
Importance of Combined Approach
A combined approach of investigations, including cytological grading of Hashimoto's thyroiditis, USG, TFT levels, and thyroid antibodies, can detect hypothyroid and subclinical hypothyroid or euthyroid state of Hashimoto's thyroiditis and provide an appropriate guide to therapy 5