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IFCC international conventional reference procedure for the measurement of free thyroxine in serum

International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Working Group for Standardization of Thyroid Function Tests (WG-STFT)1)
  • Sofie K. Van Houcke , Katleen Van Uytfanghe , Eri Shimizu , Wataru Tani , Masao Umemoto and Linda M. Thienpont
Published/Copyright: June 21, 2011
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Clinical Chemistry and Laboratory Medicine (CCLM)
From the journal Clinical Chemistry and Laboratory Medicine (CCLM) Volume 49 Issue 8

Abstract

The IFCC Working Group for Standardization of Thyroid Function Tests proposes a candidate international conventional reference procedure (RMP) for measurement of the amount-of-substance concentration of free thyroxine in plasma/serum at physiological pH 7.40 and temperature (37.0°C). The unit for reporting measurement results is, by convention, pmol/L. The RMP is based on equilibrium dialysis isotope dilution-liquid chromatography/tandem mass spectrometry (ED-ID-LC/tandem MS). The rationale for proposing a conventional RMP is that, because of the physical separation step, it is unknown whether the measurement truly reflects the concentration of free thyroxine (FT4) in serum. Therefore, the ED part of the RMP has to strictly adhere to the following conditions: use of a dialysis buffer with a biochemical composition resembling the ionic environment of serum/plasma as closely as possible; buffering of the sample to a pH of 7.40 (at 37.0°C) before dialysis, however, without additional dilution; dialysis in a device with a dialysand/dialysate compartment of identical volume and separated by a membrane of regenerated cellulose and adequate cut-off; thermostatic control of the temperature during dialysis at 37.0°C±0.50°C. The convention does not apply to the ID-LC/tandem MS part, provided it is eligible to be nominated for review by the Joint Committee for Traceability in Laboratory Medicine. Here, we describe the ED procedure, inclusive its validation and transferability, in greater detail. We recommend a protocol for successful calibration, measurement and monitoring of the accuracy/trueness and precision of the candidate conventional RMP. For details on our ID-LC/tandem MS procedures, we refer to the Supplement.

Keywords: equilibrium dialysis; isotope dilution-liquid chromatography-mass spectrometry; pH 7.40; physiological conditions; temperature 37.0°C
Corresponding author: Prof. Linda M. Thienpont, Laboratory for Analytical Chemistry, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium Phone: +32-9-264-81-04, Fax: +32-9-264-81-98
Received: 2011-03-14
Accepted: 2011-03-28
Published Online: 2011-06-21
Published in Print: 2011-08-01

©2011 by Walter de Gruyter Berlin Boston

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https://doi.org/10.1515/CCLM.2011.639
Keywords for this article
equilibrium dialysis; isotope dilution-liquid chromatography-mass spectrometry; pH 7.40; physiological conditions; temperature 37.0°C

Articles in the same Issue

  1. Editorial
  2. Pneumatic tube delivery systems for patient samples: evidence of quality and quality of evidence
  3. Reviews
  4. Translating pharmacogenetics into clinical practice: interleukin (IL)28B and inosine triphosphatase (ITPA) polymophisms in hepatitis C virus (HCV) infection
  5. New biomarkers for acute renal injury
  6. Minireview
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  8. Opinion Paper
  9. International Osteoporosis Foundation and International Federation of Clinical Chemistry and Laboratory Medicine Position on bone marker standards in osteoporosis
  10. Guidelines and Recommendations
  11. IFCC international conventional reference procedure for the measurement of free thyroxine in serum
  12. Genetics and Molecular Diagnostics
  13. Improving clinical laboratory efficiency: a time-motion evaluation of the Abbott m2000 RealTime and Roche COBAS AmpliPrep/COBAS TaqMan PCR systems for the simultaneous quantitation of HIV-1 RNA and HCV RNA
  14. Enhanced frequency of CFTR gene variants in couples who are candidates for assisted reproductive technology treatment
  15. Customer satisfaction survey to improve the European cystic fibrosis external quality assessment scheme
  16. General Clinical Chemistry and Laboratory Medicine
  17. Effect of sample collection, temperature and time of storage on β-galactosidase and total hexosaminidase activities in dried blood collected on filter paper
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  20. The utility of six over-the-counter (home) pregnancy tests
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  23. Cerebrospinal fluid findings in infants with pertussis or parapertussis1)
  24. Calcium pyrophosphate and monosodium urate crystals in synovial fluid as a cause of pseudoeosinophilia
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  26. Dual activity of serum lipoprotein-associated phospholipase A2 yielding positive and inverse associations with cardiometabolic risk
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