Measurement of free thyroxine in laboratory medicine – proposal of measurand definition

Thienpont, Linda M.; Beastall, G. H.; Christofides, Nicos; Faix, James D.; Ieiri, Tamio; Miller, W. Greg; Miller, R. W.; Nelson, Jerald C.; Ross, H. Alec; Ronin, Catherine; Rottmann, Michael; Thijssen, J. H. H.; Toussaint, B.

doi:10.1515/cclm.2007.099

Cited by 25 publications

(8 citation statements)

References 3 publications

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“…There are also ongoing efforts to redetermine the cut‐off ranges for measuring thyroid antibodies (221) and to standardise reference methods used to determine free thyroxine (222). Continued improvement in laboratory measurement techniques, and changing reference ranges, will help increase knowledge of normal thyroid hormone function, and may have significant clinical implications.…”

Section: Changing Perspectives Of Normal Thyroid Laboratory Valuesmentioning

confidence: 99%

The Thyroid‐Brain Interaction in Thyroid Disorders and Mood Disorders

Bauer

Goetz

Glenn³

et al. 2008

J Neuroendocrinology

352

230

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Thyroid hormones play a critical role in the metabolic activity of the adult brain, and neuropsychiatric manifestations of thyroid disease have long been recognised. However, it is only recently that methodology such as functional neuroimaging has been available to facilitate investigation of thyroid hormone metabolism. Although the role of thyroid hormones in the adult brain is not yet specified, it is clear that without optimal thyroid function, mood disturbance, cognitive impairment and other psychiatric symptoms can emerge. Additionally, laboratory measurements of peripheral thyroid function may not adequately characterise central thyroid metabolism. Here, we review the relationship between thyroid hormone and neuropsychiatric symptoms in patients with primary thyroid disease and primary mood disorders.

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Section: Changing Perspectives Of Normal Thyroid Laboratory Valuesmentioning

confidence: 99%

The Thyroid‐Brain Interaction in Thyroid Disorders and Mood Disorders

Bauer

Goetz

Glenn³

et al. 2008

J Neuroendocrinology

352

230

View full text Add to dashboard Cite

show abstract

“…Tandem mass spectrometric methods employing either ultrafiltration or equilibrium dialysis and which permit the simultaneous measurement of free T4 and free T3 have been published by groups working at Georgetown University and ARUP laboratories [6, 9, 31, 40]. A procedure based on equilibrium dialysis combined with determination of thyroxine in the dialysate with a trueness-based measurement procedure has been proposed but not validated as a candidate international conventional reference measurement [38, 41]. …”

Section: Tandem Mass Spectrometrymentioning

confidence: 99%

Thyroid hormone testing by tandem mass spectrometry

Soldin

2011

Clinical Biochemistry

116

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In the euthyroid person, absolute free thyroxine concentrations remain constant and correlate with the tissue hormone level, its biologic effect and the metabolic status of the patient. However, most circulating thyroid hormone is bound to plasma proteins and only a minute amount is in the unbound free form. Studies have shown that current free thyroxine immunoassays are binding protein dependent. Novel high-performance liquid chromatography tandem mass spectrometry (LC/MS/MS) methods have successfully dealt with problems inherent in many immunoassays for thyroid hormones and afforded improved specificity and accuracy in thyroid hormone measurements. We emphasize problems with thyroid hormone testing employing immunoassays including direct and indirect thyroid hormone immunoassays, sample processing, methods of free hormone separation and review the emerging role of liquid chromatography-tandem mass spectrometry in thyroid hormone testing. The latest generation of tandem mass spectrometers has superior limits of quantification, permitting omission of previously employed derivatization steps. Liquid chromatography-tandem mass spectrometry affords the specificity, precision, and limits of quantification necessary for the reliable measurement of thyroid hormones, enhancing diagnostic capabilities, and affording the profiles of the iodothyronines and thyronamines. These methods are especially important in states of disease and during pregnancy when protein binding is a factor that interferes with other methods for thyroid hormone analysis.

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“…70 Although the measurement of total serum thyroxine and triiodothyronine have been standardized, 71 free thyroid hormone measurements are problematic because measurement conditions, such as pH and temperature, affect the free/protein-bound hormone equilibrium. 72 However an international conventional reference measurement procedure and a secondary calibrator have been validated. 73,74 For measurands yet to be adequately defined, traceability to non-SI measurement units can improve the harmonization of patients' results, providing the conventional calibrators are commutable with the routine measurement procedures in use.…”

Section: White Metrological Traceabilitymentioning

confidence: 99%

Metrological traceability in clinical biochemistry

White

2011

Ann Clin Biochem

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True and precise routine measurements of quantities of clinical interest are essential if results are to be optimally interpreted for patient care. Additionally, results produced by different measurement procedures for the same measurand must be comparable if common diagnostic decision values and clinical research findings are to be broadly applied. Metrology, the science of measurement, provides laboratory medicine with a structured approach to the development and terminology of reference measurement systems which, when implemented, improve the accuracy and comparability of patients' results. The metrological approach is underpinned by the concepts of common measurement units, traceability of measured values, measurement uncertainty and commutability. Where traceability to the International System of Units (SI units) is not yet realized for a measurand, result comparability may be achievable by other, less ideal, approaches. Measurements are the core activity of clinical laboratories, and clinical biochemists should ensure that patients' results are traceable to the highest available reference. This review introduces and illustrates the principles of metrological traceability, describes its critical importance to improving the quality of patients' results and highlights the need to actively promote traceability in clinical laboratories.

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Measurement of free thyroxine in laboratory medicine – proposal of measurand definition

Cited by 25 publications

References 3 publications

The Thyroid‐Brain Interaction in Thyroid Disorders and Mood Disorders

The Thyroid‐Brain Interaction in Thyroid Disorders and Mood Disorders

Thyroid hormone testing by tandem mass spectrometry

Metrological traceability in clinical biochemistry

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