Evaluation of harmonization among thyroid hormone testing systems: A comparative study based on external quality assessment data.

Objective: To evaluate thyroid hormone test harmonization using external quality assessment (EQA) data, guiding laboratory quality enhancement and big data interoperability.

Methods: EQA data for T3, T4, FT3, FT4, and TSH from January 2022 to December 2024 were collected. We calculated the total allowable error for both our laboratory (TEa-Lab) and peer groups (TEa-peer) using bias and coefficient of variation data. We derived harmonization indices (HI) by comparing TEa values against three biological variation thresholds (minimum, desirable, and optimal). An HI value ≤ 1 indicated satisfactory harmonization.

Results: The TSH test in our laboratory showed desirable harmonization; however, the HI for T3, T4, FT3, and FT4 ranged from 1.1 to 1.9, failing to reach the minimum harmonization level. Among the peer group tests, the level of coordination of each analysis system varies, and the harmonization levels ranging from below the minimum to the optimal harmonization level, even failing to reach the minimum level. The harmonization level of thyroid hormones between our laboratory and peer groups showed strong consistency.

Conclusion: The HI values quantitatively calculated from EQA data accurately reflect the harmonization level between thyroid hormone testing systems in the laboratory and peer groups. This helps identify laboratory issues and implement corrective actions, providing a reference for laboratory big data interoperability and clinical decision-making.