Feasibility Study of the Use of Frozen Human Sera in Split-Sample Comparison of Immunoassays With Reference Measurement Procedures for Total Thyroxine and Total Triiodothyronine Measurement
Linda M. Thienpont, Katleen Van Uytfanghe, J Marriot, Y Tokura, Lothar Siekmann, Anja Kessler, David M. Bunk, Susan Tai
Background: Diagnostic manufacturers must ensure/document metrologically traceable assays. Here we report on a feasibility study that investigated the use of a split-sample comparison with processed, frozen single-donation sera assigned with target values by reference measurement procedures (RMPs). Immunoassays for total thyroxine (TT4) and triiodothyronine (TT3) were taken as a model. Methods: Two panels of sera were quantified for TT4 and TT3 with validated RMPs and measured in parallel with several immunoassays. The results were interpreted in terms of traceability of calibration (trueness) and of the individual measurement result (accuracy) by linear regression analysis and graphical representation against specifications. The commutability of the sera was investigated by analysis of TT4 in the processed sera in parallel with freshly collected but non-filtered specimens. Results: The TT4 (TT3) concentrations in the sera (according to the RMPs) spanned a measurement range from 64 nmol/L to 269 nmol/L (0.88 nmol/L to 13.7 nmol/L). The method comparison showed that for TT4 the routine results agreed on average with the RMPs' values, whereas for TT3, they were typically higher. In addition, it demonstrated for both TT4 and TT3 there was a considerable between-assay divergence in traceability of calibration and accuracy. However, the evidence of non-commutability of the sera due to processing indicates that the interpretation of this study should be treated with caution. Conclusions: The feasibility study showed that for documenting/validating traceability of total thyroid measurements frozen single-donation sera principally can serve the purpose. However, the way in which the sera are processed requires in-depth investigation in order not to jeopardize commutability.
, Van Uytfanghe, K.
, Marriot, J.
, Tokura, Y.
, Siekmann, L.
, Kessler, A.
, Bunk, D.
and Tai, S.
Feasibility Study of the Use of Frozen Human Sera in Split-Sample Comparison of Immunoassays With Reference Measurement Procedures for Total Thyroxine and Total Triiodothyronine Measurement, Clinical Chemistry
(Accessed December 7, 2023)