Evaluation of Analytical Performance and Reference Interval of Abbott Thyroglobulin (Tg) Chemiluminescent Microparticle Immunoassay (CMIA) in a Chinese Population.

Objective: Accurate measurement of thyroglobulin (Tg) is crucial for managing patients with differentiated thyroid cancer (DTC). This study aims to verify the analytical performance of the Abbott Tg assay and establish Tg reference intervals in an apparently healthy Chinese population.

Methods: Analytical performance was evaluated in terms of precision, detection capabilities, and linearity. A method comparison with the Roche Tg assay was conducted using Passing-Bablok regression and Bland-Altman analysis. Reference intervals were established using serum Tg levels measured by the Abbott Alinity system in 1,081 healthy volunteers, categorized by age and gender.

Results: Repeatability (CV%) for Tg at 0.96 and 7.53 ng/mL was 1.7% and 1.44%, respectively. Within-laboratory imprecision (CV%) at these concentrations were 2.17% and 1.61%. All test results (100%) were at or below the claimed limits of blank (LoB) and detection (LoD), exceeding the 85% threshold for the critical value observation ratio. The CV for the limit of quantification (LoQ) was 6.94%. Passing-Bablok and Bland-Altman analyses for Abbott vs. Roche Tg assays revealed a y-intercept of 0.025, a slope of 0.981, and a Spearman rank correlation coefficient of 0.993 (P<0.0001), with a negative bias of -3.7%. Reference intervals were set between 0.22 and 53.30 ng/mL (2.5^th-97.5^th percentile). Gender had no impact on Tg levels while significant differences were found across different age groups (P=0.008).

Conclusion: The Abbott Tg assay demonstrates verified analytical performance as per the manufacturer's claims. Reference intervals were established for an apparently healthy Chinese population, highlighting the significant influence of age on serum Tg levels.