Report of the IFCC Working Group for Standardization of Thyroid Function Tests; Part 3: Total Thyroxine and Total Triiodothyronine

Thienpont, Linda M.; Uytfanghe, Katleen Van; Beastall, G. H.; Faix, James D.; Ieiri, Tamio; Miller, W. Greg; Nelson, Jerald C.; Ronin, Catherine; Ross, H. Alec; Thijssen, J. H. H.; Toussaint, B.

doi:10.1373/clinchem.2009.140228

Cited by 52 publications

(19 citation statements)

References 35 publications

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“…The TSH, TT4, total triiodothyronine (TT3), FT4 and FT3 ranges have been shown to vary slightly depending on different methods of analysis, although this variation is not clinically significant [32][33][34].…”

Section: Main Issuementioning

confidence: 99%

Evaluation of Pregnancy and Thyroid Function

Chang-Eun

2018

Korean J Clin Lab Sci.

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임신과 갑상선 기능의 평가 박창은 남서울대학교 임상병리학과, 분자진단연구소During early pregnancy, before the development of a functioning thyroid gland, thyroid stimulating hormone (TSH) is a very sensitive marker of thyroid dysfunction during pregnancy. Normal values have been modified during gestation with a downward shift. The fetus is influenced by the TSH supplied by the mother. TSH and free thyroxine (FT4) concentrations vary during pregnancy and conventional units can vary between laboratories. A downward shift of the TSH reference range occurs during pregnancy, with a decrease in both the lower and upper limits of maternal TSH, relative to the typical non-pregnant TSH reference range. Each laboratory produces its own reference TSH and FT4 concentrations because there are many different assays that yield different results in pregnancy. Therefore, automated immunoassays used for serum FT4 analysis are still used widely, but the important considerations discussed above must be noted. The use of population-based, trimester-specific reference ranges remains the best way to handle this issue The slight downward shift in the upper reference range of TSH occurring in the latter first trimester (7∼12 weeks) of pregnancy, typically not observed prior to 7 weeks. Their use indicates high or low levels in a quantitative manner independent of the reference ranges. These data highlight the importance of calculating population-based pregnancy-specific thyroid parameter reference intervals. A precision medicine initiative in this area will require the collection and analysis of a large number of genetic, biological, psychosocial, and environmental variables in large cohorts of individuals. Large prospective randomized controlled trials will be needed to resolve these controversies.

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Section: Main Issuementioning

confidence: 99%

Evaluation of Pregnancy and Thyroid Function

Chang-Eun

2018

Korean J Clin Lab Sci.

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“…This protocol has also been validated to be suitable for triglycerides and HDL cholesterol (15 ) and for creatinine (16 ). The C37A protocol has not been validated to produce samples that are commutable with patient samples for other analytes but represents the best available approach and has been used to prepare single-donor serum samples and pools for several investigations of the trueness of measurement procedures for several analytes (17)(18)(19)(20)(21). Thienpont et al found that processing of serum (e.g., sterile filtration, storage before aliquoting and freezing) may disturb the equilibrium between free and protein-bound thyroid hormone and hence jeopardize the commutability of a reference material prepared even from sera that has been subjected to minimal processing (22 ).…”

Section: Preparation Of Samples Intended To Be Commutablementioning

confidence: 99%

Proficiency Testing/External Quality Assessment: Current Challenges and Future Directions

et al. 2011

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BACKGROUND: Proficiency testing (PT), or external quality assessment (EQA), is intended to verify on a recurring basis that laboratory results conform to expectations for the quality required for patient care.CONTENT: Key factors for interpreting PT/EQA results are knowledge of the commutability of the samples used and the process used for target value assignment. A commutable PT/EQA sample demonstrates the same numeric relationship between different measurement procedures as that expected for patients' samples. Noncommutable PT/EQA samples frequently have a matrix-related bias of unknown magnitude that limits interpretation of results. PT/EQA results for commutable samples can be used to assess accuracy against a reference measurement procedure or a designated comparison method. In addition, the agreement of the results between different measurement procedures for commutable samples reflects that which would be seen for patients' samples. PT/EQA results for noncommutable samples must be compared to a peer group mean/ median of results from participants who use measurement procedures that are expected to have the same or very similar matrix-related bias. Peer group evaluation is used to asses whether a laboratory is using a measurement procedure in conformance to the manufacturer's specifications and/or in conformance to other laboratories using the same technology. A noncommutable PT/EQA sample does not give meaningful information about the relationship of results for patients' samples between different measurement procedures.

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“…The IFCC Committee for Standardization of Thyroid Function Tests (C-STFT) aims at equivalence of laboratory testing for total and free thyroid hormones and thyrotropin (TSH) [12,13,14]. The committee was established in light of the prevalence of thyroid disease, the frequency of laboratory testing, and multiple reports on discrepant measurement results.…”

Section: Introductionmentioning

confidence: 99%

“…The committee was established in light of the prevalence of thyroid disease, the frequency of laboratory testing, and multiple reports on discrepant measurement results. For total thyroxine/triiodothyronine testing, a state-of-the-art SI-traceable reference measurement system was already available for implementation [14]. For free thyroid hormones and TSH, the C-STFT had to start the process from scratch.…”

Section: Introductionmentioning

confidence: 99%

A Progress Report of the IFCC Committee for Standardization of Thyroid Function Tests

et al. 2014

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Background: The IFCC Committee for Standardization of Thyroid Function Tests aims at equivalence of laboratory test results for free thyroxine (FT4) and thyrotropin (TSH). Objectives: This report describes the phase III method comparison study with clinical samples representing a broad spectrum of thyroid disease. The objective was to expand the feasibility work and explore the impact of standardization/harmonization in the clinically relevant concentration range. Methods: Two sets of serum samples (74 for FT4, 94 for TSH) were obtained in a clinical setting. Eight manufacturers participated in the study (with 13 FT4 and 14 TSH assays). Targets for FT4 were set by the international conventional reference measurement procedure of the IFCC; those for TSH were based on the all-procedure trimmed mean. The manufacturers recalibrated their assays against these targets. Results: All FT4 assays were negatively biased in the mid- to high concentration range, with a maximum interassay discrepancy of approximately 30%. However, in the low range, the maximum deviation was approximately 90%. For TSH, interassay comparability was reasonable in the mid-concentration range, but worse in the pathophysiological ranges. Recalibration was able to eliminate the interassay differences, so that the remaining dispersion of the data was nearly entirely due to within-assay random error components. The impact of recalibration on the numerical results was particularly high for FT4. Conclusions: Standardization and harmonization of FT4 and TSH measurements is feasible from a technical point of view. Because of the impact on the numerical values, the implementation needs careful preparation with the stakeholders.

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Report of the IFCC Working Group for Standardization of Thyroid Function Tests; Part 3: Total Thyroxine and Total Triiodothyronine

Cited by 52 publications

References 35 publications

Evaluation of Pregnancy and Thyroid Function

Evaluation of Pregnancy and Thyroid Function

Proficiency Testing/External Quality Assessment: Current Challenges and Future Directions

A Progress Report of the IFCC Committee for Standardization of Thyroid Function Tests

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