Diagnostic Dilemma in Discordant Thyroid Function Tests Due to Thyroid Hormone Autoantibodies

Area of Science:

• Clinical Chemistry
• Endocrinology
• Immunology

Background:

• Assay interference is a potential cause of abnormal thyroid function tests.
• Prompt identification of interference is crucial to prevent incorrect patient management.

Purpose of the Study:

• To present a case of discordant thyroid function tests across different assay platforms.
• To investigate the role of thyroid autoantibodies in causing immunoassay interference.

Main Methods:

• Case presentation of a patient with autoimmune thyroid disease.
• Laboratory data analysis including thyroid function tests on multiple platforms.
• Investigation into immunoassay interference mechanisms.

Main Results:

• A 21-year-old woman with hypothyroidism on levothyroxine presented with elevated thyroid hormones but normal TSH.
• Thyroid function tests showed discrepant results across different assay platforms.
• Positive thyroid hormone autoantibodies (THAAbs) were identified as the cause of interference.

Conclusions:

• Thyroid hormone autoantibodies (THAAbs) can cause abnormal thyroid function tests.
• THAAbs interfere with immunoassays, leading to results inconsistent with clinical presentation.
• Early recognition of THAAbs is essential to avoid inappropriate patient management.