Report of the IFCC Working Group for Standardization of Thyroid Function Tests; Part 2: Free Thyroxine and Free Triiodothyronine

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

doi:10.1373/clinchem.2009.140194

Cited by 116 publications

(100 citation statements)

References 7 publications

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“…This assay has proven to give comparable results with other assays, according to the report from the IFCC WG for standardization of thyroid function tests (17).…”

Section: Biochemical Determinationsmentioning

confidence: 78%

Thyroid hormone status within the physiological range affects bone mass and density in healthy men at the age of peak bone mass

Roef

Lapauw

Goemaere

et al. 2011

European Journal of Endocrinology

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Context: The hormonal factors involved in the regulation of peak bone mass (PBM) in men have not been fully investigated. Apart from gonadal steroids and somatotropic hormones, thyroid hormones are known to affect bone maturation and homeostasis and are additional candidate determinants of adult bone mass. Objective: We aimed to investigate between-subject physiological variation in free and total thyroid hormone concentrations, TSH, and thyroid binding globulin (TBG) in relation to parameters of bone mass, geometry, and mineral density in healthy men at the age of PBM. Design and setting: We recruited 677 healthy male siblings aged 25-45 years in a cross-sectional, population-based study. Areal and volumetric bone parameters were determined using dual-energy x-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). Total and free thyroid hormones, TBG, and TSH were determined using immunoassays. Results: Free and total thyroid hormone concentrations were inversely associated with bone mineral density (BMD) and bone mineral content (BMC) at the hip and total body (free triiodothyronine (FT 3 ), total T 3 (TT 3 ), and total T 4 (TT 4 )) and at the spine (FT 3 ). TBG was negatively associated with BMC and areal BMD at all sites. At the radius, cortical bone area was inversely associated with TT 3 , TT 4 , and TBG, and trabecular bone density was inversely associated with free thyroxine, TT 4 , and TBG. We observed inverse associations between cortical bone area at the mid-tibia and FT 3 , TT 3 , TT 4 , and TBG. No associations between TSH and DXA or pQCT measurements were found. Conclusion: In healthy men at the age of PBM, between-subject variation in thyroid hormone concentrations affects bone density, with higher levels of FT 3 , TT 3 , TT 4 , and TBG being associated with less favorable bone density and content.

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“…This assay has proven to give comparable results with other assays, according to the report from the IFCC WG for standardization of thyroid function tests (17).…”

Section: Biochemical Determinationsmentioning

confidence: 78%

Thyroid hormone status within the physiological range affects bone mass and density in healthy men at the age of peak bone mass

Roef

Lapauw

Goemaere

et al. 2011

European Journal of Endocrinology

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“…44 To address this important issue, a working group for the international standardization of the free T4 assay has been formed. [45][46][47] Thus, if the assessment of free T4 may not be necessary in many cases (low pre-test probability), and the reliability is limited, there is likely to be a substantial number of false-positive results.…”

Section: Free Thyroxine (Free T4)mentioning

confidence: 99%

“…43,44,47 Measurement of free T4 by equilibrium dialysis is considered the gold standard but, it is of limited availability to most providers. There is good correlation of free T4 by equilibrium dialysis and free T4 by liquid chromatography-tandem mass spectrometry (LC-MS/MS).…”

Section: Free Thyroxine (Free T4)mentioning

confidence: 99%

Biochemical Testing of the Thyroid: TSH is the Best and, Oftentimes, Only Test Needed – A Review for Primary Care

Sheehan

2016

Clin Med Res

140

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Disorders of thyroid function are common, and screening, diagnosis, and management are often performed by primary care providers. While management of significant biochemical abnormalities is reasonably straight forward, laboratory tests only slightly outside, or even within, the normal range are becoming more difficult to appropriately manage. A large part of this increasing difficulty in appropriate management is caused by patients requesting, and even demanding, certain tests or treatments that may not be indicated. Symptoms of thyroid dysfunction are non-specific and extremely prevalent in the general population. This, along with a growing body of information available to patients via the lay press and internet suggesting that traditional thyroid function testing is not reliable, has fostered some degree of patient mistrust. Increasingly, when a physician informs a patient that their thyroid is not the cause of their symptoms, the patient is dissatisfied and even angry. This review aims to clarify the interpretation of normal and mild abnormalities of thyroid function tests by describing pituitarythyroid physiology and through an in depth review of, arguably, the three most important biochemical tests of thyroid function: TSH, free T4, and anti-TPO antibodies. It is important for primary care providers to have an understanding of the shortcomings and proper interpretation of these tests to be better able to discuss thyroid function with their patients.

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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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Report of the IFCC Working Group for Standardization of Thyroid Function Tests; Part 2: Free Thyroxine and Free Triiodothyronine

Abstract: BACKGROUND:Free thyroxine (FT4) and free triiodothyronine (FT3) measurements are useful in the diagnosis and treatment of a variety of thyroid disorders. The IFCC Scientific Division established a Working Group to resolve issues of method performance to meet clinical requirements.

Cited by 116 publications

References 7 publications

Thyroid hormone status within the physiological range affects bone mass and density in healthy men at the age of peak bone mass

Thyroid hormone status within the physiological range affects bone mass and density in healthy men at the age of peak bone mass

Biochemical Testing of the Thyroid: TSH is the Best and, Oftentimes, Only Test Needed – A Review for Primary Care

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

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