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This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: clinchem.2005.058180v1 51/12/2303    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Thienpont, L. M. Articles by Tai, S. Search for Related Content PubMed PubMed Citation Articles by Thienpont, L. M. Articles by Tai, S. Related Collections Endocrinology and Metabolism

Feasibility Study of the Use of Frozen Human Sera in Split-Sample Comparison of Immunoassays with Candidate Reference Measurement Procedures for Total Thyroxine and Total Triiodothyronine Measurements

¹ Laboratory for Analytical Chemistry, Faculty of Pharmaceutical Sciences, Ghent University, Gent, Belgium.
² LGC, Teddington, United Kingdom.
³ Institute for Clinical Biochemistry, University of Bonn, Bonn, Germany.
⁴ National Institute of Standards and Technology, Gaithersburg, MD.

^aAddress correspondence to this author at: Laboratory for Analytical Chemistry, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000 Gent, Belgium. Fax 32-9-264-81-98; e-mail linda.thienpont{at}ugent.be.

Background: Diagnostic manufacturers must ensure/document metrologically traceable assays. We report on a feasibility study of a split-sample comparison for that purpose. Processed, frozen single-donation sera, assigned target values by candidate reference measurement procedures (cRMPs), were used with immunoassays for total thyroxine (TT₄) and triiodothyronine (TT₃) as models.

Methods: Two serum panels were quantified for TT₄ and TT₃ with validated cRMPs and measured in parallel with at least 14 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 parallel analysis of TT₄ in freshly collected but nonfiltered specimens.

Results: The TT₄ (TT₃) concentrations in the sera (according to the cRMPs) were 64–269 nmol/L (0.88–13.7 nmol/L). The method comparison showed that for TT₄, on average, the immunoassays produced results in agreement with the cRMPs, whereas for TT₃, results were typically higher. It also demonstrated a considerable between-assay divergence in traceability of calibration and accuracy. The evidence of noncommutability of the sera attributable to processing, however, indicates that the interpretation should be treated with caution.

Conclusions: Frozen sera can be used for documenting/validating traceability of total thyroid measurements. The way in which the sera are processed may jeopardize commutability, however, and therefore requires in-depth investigation.

The following articles in journals at HighWire Press have cited this article:

				H. W. Vesper and L. M. Thienpont Traceability in Laboratory Medicine Clin. Chem., June 1, 2009; 55(6): 1067 - 1075. [Abstract] [Full Text] [PDF]

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