B-021 Analytical Performance of Thyroid Function Test on DxI800 System

Abstract

Abstract Background Thyroid function tests (TFT) which usually include thyroid stimulating hormone (TSH), total triiodothyronine (TT3), and free thyroxine (FT4) are widely applied in clinical practice for screening, diagnosis and monitoring of thyroid disease. We evaluated analytical performance of TSH, TT3, and FT4 using DxI800 (Beckman Coulter, USA) including comparison to Alinity I (Abbott, USA). Methods Precision was determined by percent coefficient of variation (%CV) measuring low, medium, and high levels of quality control material for 5 days with one run per day, 5 replicates per run. Linearity was evaluated using 5 levels of patient serum samples and concentrations were determined by the mean value of two replicates of each level. Method comparison was performed by Passing-Bablok regression using 40 patient serum samples. Results The within-run imprecision at low, medium and high level were 1.50%, 1.77%, and 2.59% for TSH; 4.10%, 2.45%, and 2.84% for TT3; and 3.23%, 2.76%, and 2.19% for FT4. The within-laboratory imprecision at low, medium, and high level were 1.61%, 1.91%, and 2.87% for TSH; 4.33%, 3.73%, and 3.70% for TT3; and 3.36%, 2.76%, and 2.20% for FT4. Linearity of TFT on DxI800 was demonstrated in the range of 0.01–44.68 µIU/mL, 0.09–7.40 ng/mL, and 0.18–5.52 ng/dL for TSH, TT3, and FT4, respectively. Method comparison between DxI800 and Alinity I showed a slope of 1.21 and intercept of 0.05 (correlation coefficient R = 0.994); a slope of 0.95 and intercept of 0.13 (correlation coefficient R = 0.971); and a slope of 1.81 and intercept of −0.88 (correlation coefficient R = 0.969) for TSH, TT3, and FT4, respectively. Conclusion DxI800 showed acceptable performance in terms of precision and linearity for TFT assay including TSH, TT3, and FT4. This study demonstrated that TFT on DxI800 are suitable in clinical laboratory.