TSH Receptor Antibody Test Utilization Patterns From a National Reference Laboratory: TRAb, TSI, or Both?

Area of Science:

• Endocrinology
• Clinical Chemistry
• Immunodiagnostics

Background:

• Two classes of TSHR antibody assays exist: TRAb and TSI.
• Clinical guidelines lack specificity for TSHR autoantibody test selection in hyperthyroidism diagnosis.
• This leads to paired testing, discordant results, and increased healthcare expenditure.

Purpose of the Study:

• To evaluate the clinical and analytical redundancy of paired TRAb and TSI assays for diagnosing autoimmune hyperthyroidism.
• To analyze the frequency of paired orders, assay concordance, and clinical correlation.
• To estimate the financial impact of unnecessary paired testing.

Main Methods:

• Analysis of over 189,000 patient encounters with TRAb and TSI bioassay (TSI-BA) or bridge immunoassay (TSI-Br) orders.
• Assessment of paired order frequency and qualitative agreement between TRAb and TSI.
• Chart review for clinical correlation and cost analysis of paired testing.

Main Results:

• TRAb and TSI were co-ordered in 14.3% (TSI-BA) and 17.4% (TSI-Br) of encounters.
• Discordance was observed in 12.5% (TSI-BA) and 6.6% (TSI-Br) of paired orders.
• TSI assays showed better alignment with hyperthyroidism and Graves' disease diagnoses; paired testing increased costs by 31%–325%.

Conclusions:

• Paired TRAb and TSI testing for autoimmune hyperthyroidism is largely redundant.
• A single TSHR antibody assay is sufficient for most diagnostic scenarios.
• Streamlining TSHR antibody testing can lead to significant healthcare cost savings.