donderdag 17 augustus 2017

Standaardisatie van schildklierfunctie tests gewenst deel 3

The IFCC Committee for Standardization of Thyroid Function Tests intended to standardize free thyroxine (FT4) immunoassays. They developed a Système International d'Unités traceable conventional reference measurement procedure (RMP) based on equilibrium dialysis and mass spectrometry. They describe here the latest studies intended to recalibrate against the RMP and supply a proof of concept, which should allow continued standardization efforts.

Standardization of free thyroxine (FT4) measurements allows the adoption of a more uniform reference interval
Linde A.C. De Grande, Katleen Van Uytfanghe, Dries Reynders, Barnali Das, James D. Faix, Finlay MacKenzie, Brigitte Decallonne, Akira Hishinuma, Bruno Lapauw, Paul Taelman, Paul Van Crombrugge, Annick Van den Bruel, Brigitte Velkeniers, Paul Williams, Linda M. Thienpont

Standaardisatie van schildklierfunctie tests gewenst deel 1

Standaardisatie van schildklierfunctie tests gewenst deel 2

De Grande et al. used the RMP to target the standardization and reference interval (RI) panels, which were also measured by 13 manufacturers. They validated the suitability of the recalibrated results to meet specifications for bias (3.3%) and total error (8.0%) determined from biological variation. However, because these specifications were stringent, they expanded them to 10% and 13%, respectively. The results for the RI panel were reported as if the assays were recalibrated. They estimated all but 1 RI using parametric statistical procedures and hypothesized that the RI determined by the RMP was suitable for use by the recalibrated assays.


Twelve of 13 recalibrated assays had a bias, meeting the 10% specification with 95% confidence; for 7 assays, this applied even for the 3.3% specification. Only 1 assay met the 13% total error specification. Recalibration reduced the CV of the assay means for the standardization panel from 13% to 5%. The proof-of-concept study confirmed their hypothesis regarding the RI but within constraints.


Recalibration to the RMP significantly reduced the FT4 immunoassay bias, so that the RI determined by the RMP was suitable for common use within a margin of 12.5%.

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