Endocrine Abstracts

Background: Diagnosis and monitoring of thyroid diseases rely on thyroid function tests. Testing for Thyroid Stimulating Hormone (TSH) and free thyroxin (FT4) are frontline assays for the diagnosis of hyper- and hypothyroidism. Measurement of TSH receptor autoantibodies (TRAB) is pivotal for the diagnosis of Graves’ disease. Our study objective was to determine the performances of ABEI-based automated immunoassays for measurement of TSH, FT4 and TRAb.

Methods: Performances of the Maglumi^® 800 TSH, FT4 and TRAb chemiluminescent immunoassays that applies ABEI labels were determined. Imprecision of assays was assessed with control materials. Method comparison was performed with Cobas electrochemiluminescent assays for TSH and FT4 and with Kryptor Compact Plus assay for TRAb. Reference intervals were also confirmed with samples from healthy volunteers.

Results: Between-run imprecision coefficients of variation were 7.1% for concentrations of 3.3 IU/ml for TSH, 4.4% for concentrations of 15.0 pg/ml for FT4 and 2.2 % for concentrations of 3.6 IU/l for TRAb, respectively. Passing-Bablok regression analysis showed a slope of 1.07 and an intercept of -0.06 for TSH, a slope of 1.03 and an intercept of 0.99 for FT4. For TRAb assay, the Kappa coefficient of concordance with the TRAK method was 0.79. Reference intervals were 0.4 – 2.6 IU/ml for TSH and 8.0 to 17 pg/ml for FT4. The 99^th percentile of the reference of the TRAb assay was 1.38 IU/ml.

Conclusions: The ABEI-based automated immunoassays showed good analytical performances for the Maglumi^® TSH, FT4 and TRAb and our study confirmed reference intervals for those assays.