Abstract

Background: The purpose of an external quality assessment (EQA) is to evaluate the analytical capability of clinical laboratories, identify differences among the laboratories and improve analytical quality. Our EQA results show that the rates of unsatisfactory performance for thyroid hormone tests were the highest in all of our EQA programs. Therefore, the main purpose of this study was to investigate unsatisfactory results by comparing the analytical values of five routinely used analytical systems.

Methods: The Kruskal-Wallis and two-sample Kolmogorov-Smirnov tests were used to identify analytical differences among and between analytical systems, respectively.

Results: The rates of significantly different results compared to the total number of analytical results were 81.1%, 64.5%, 93.3%, 50.0% and 56.7% for free triiodothyronine, total triiodothyronine, free thyroxine, total thyroxine and thyroid-stimulating hormone, respectively.

Conclusions: Relatively large analytical differences between analytical systems were observed, especially when the analytical systems were used to measure free thyroid hormones.

Clin Chem Lab Med 2006;44:1363–6.