Harmonization protocols for thyroid stimulating hormone (TSH) immunoassays: different approaches based on the consensus mean value

2015 ◽  
Vol 53 (3) ◽  
Author(s):  
Aldo Clerico ◽  
Andrea Ripoli ◽  
Gian Carlo Zucchelli ◽  
Mario Plebani
Keyword(s):  
Statistical Approach ◽  
External Quality Assessment ◽  
International System ◽  
Measurement Procedure ◽  
Mean Value ◽  
Thyroid Stimulating Hormone ◽  
Consensus Mean ◽  
System Of Units ◽  
Considerable Debate ◽  
Laboratory Results

AbstractThe lack of interchangeable laboratory results and consensus in current practices has underpinned greater attention to standardization and harmonization projects. In the area of method standardization and harmonization, there is considerable debate about how best to achieve comparability of measurement for immunoassays, and in particular heterogeneous proteins. The term standardization should be used only when comparable results among measurement procedures are based on calibration traceability to the International System of Units (SI unit) using a reference measurement procedure (RMP). Recently, it has been promoted the harmonization of methods for many immunoassays, and in particular for thyreotropin (TSH), as accepted RMPs are not available. In a recent paper published in this journal, a group of well-recognized authors used a complex statistical approach in order to reduce variability between the results observed with the 14 TSH immunoassay methods tested in their study. Here we provide data demonstrating that data from an external quality assessment (EQA) study allow similar results to those obtained using the reported statistical approach.

scholarly journals A new definition for the mole based on the Avogadro constant: a journey from physics to chemistry

2011 ◽  
Vol 369 (1953) ◽  
pp. 3993-4003 ◽  
Author(s):  
Martin J. T. Milton
Keyword(s):  
Measurement Uncertainty ◽  
Early Development ◽  
International System ◽  
Atomic Masses ◽  
Amount Of Substance ◽  
Avogadro Constant ◽  
System Of Units ◽  
Considerable Debate ◽  
Recent Addition ◽  
Base Units

The mole is the most recent addition to the set of base units that form the International System of Units, although its pre-cursor the ‘gram-molecule’, had been in use by both physicists and chemists for more than 120 years. A proposal has been published recently to establish a new definition for the mole based on a fixed value for the Avogadro constant. This would introduce consistent relative uncertainties for the molar and the atomic masses while making no change to the system of relative atomic masses (‘atomic weights’). Although the proposal would have little impact on the measurement uncertainty of practical work, it has stimulated considerable debate about the mole and the nature of the quantity amount of substance. In this paper, the rationale for the new definition is explained against the background of changes in the way the quantity amount of substance has been used, from its first use during the early development of thermodynamics through to the use of the ‘number of gram-molecules’ at the end of the nineteenth century.

scholarly journals The Tortuous Road to the Adoption of katal for the Expression of Catalytic Activity by the General Conference on Weights and Measures

2002 ◽  
Vol 48 (3) ◽  
pp. 586-590 ◽  
Author(s):  
René Dybkær
Keyword(s):  
Catalytic Activity ◽  
International System ◽  
Measurement Procedure ◽  
Enzymic Activity ◽  
Measuring System ◽  
Medical Laboratory ◽  
International Union ◽  
Weights And Measures ◽  
System Of Units ◽  
Global Standardization

Abstract Background: The “unit” for “enzymic activity” (U = 1 μmol/min) was recommended by the International Union of Biochemistry and Molecular Biology (IUB) in 1961 and is widely used in medical laboratory reports. The general trend in metrology, however, is toward global standardization through defining units coherent with the International System of Units (SI). Approach: Several proposals were advanced from the IFCC, International Union of Pure and Applied Chemistry, and IUB regarding the definition for enzymic activity as well as the terms for kind-of-quantity, units, symbol, and dimension. In 1977, international agreement was reached between these bodies and WHO that “catalytic activity” (z), of a catalyst in a given system is defined by the rate of conversion in a measuring system (in mol/s) and expressed in “katal” (symbol, kat; equal to 1 mol/s). The katal is invariant of the measurement procedure, but the numerical quantity value is not. Gaining support for the katal from the final arbiter, the General Conference on Weights and Measures, was slow, but Resolution 12 of 1999 adopted the katal (symbol, kat) as a special name and symbol for the SI-derived unit, mol/s, used in measuring catalytic activity. Conclusions: Laboratory results for amounts of catalysts, including enzymes, measured by their catalytic activity can now officially be expressed in katals and are traceable to the SI provided that the specified indicator reaction reflects first-order kinetics. The conversion from “unit” is: 1 U = 16.667 × 10−9 kat. Further derived quantities have coherent units such as kat/L, kat/kg, and kat/kat = 1.

scholarly journals International System of Units Traceable Results of Hg Mass Concentration at Saturation in Air from a Newly Developed Measurement Procedure

2014 ◽  
Vol 86 (15) ◽  
pp. 7819-7827 ◽  
Author(s):  
Christophe R. Quétel ◽  
Mariavittoria Zampella ◽  
Richard J. C. Brown ◽  
Hugo Ent ◽  
Milena Horvat ◽  
...  
Keyword(s):  
Mass Concentration ◽  
International System ◽  
Measurement Procedure ◽  
International System Of Units ◽  
System Of Units

scholarly journals Analytical Bias Exceeding Desirable Quality Goal in 4 out of 5 Common Immunoassays: Results of a Native Single Serum Sample External Quality Assessment Program for Cobalamin, Folate, Ferritin, Thyroid-Stimulating Hormone, and Free T4 Analyses

2016 ◽  
Vol 62 (9) ◽  
pp. 1255-1263 ◽  
Author(s):  
Gunn B B Kristensen ◽  
Pål Rustad ◽  
Jens P Berg ◽  
Kristin M Aakre
Keyword(s):  
Quality Assessment ◽  
External Quality Assessment ◽  
Measurement Procedure ◽  
Reference Intervals ◽  
Thyroid Stimulating Hormone ◽  
Free T4 ◽  
External Quality ◽  
Reference Measurement ◽  
Serum Pool ◽  
Reference Measurement Procedure

Abstract BACKGROUND We undertook this study to evaluate method differences for 5 components analyzed by immunoassays, to explore whether the use of method-dependent reference intervals may compensate for method differences, and to investigate commutability of external quality assessment (EQA) materials. METHODS Twenty fresh native single serum samples, a fresh native serum pool, Nordic Federation of Clinical Chemistry Reference Serum X (serum X) (serum pool), and 2 EQA materials were sent to 38 laboratories for measurement of cobalamin, folate, ferritin, free T4, and thyroid-stimulating hormone (TSH) by 5 different measurement procedures [Roche Cobas (n = 15), Roche Modular (n = 4), Abbott Architect (n = 8), Beckman Coulter Unicel (n = 2), and Siemens ADVIA Centaur (n = 9)]. The target value for each component was calculated based on the mean of method means or measured by a reference measurement procedure (free T4). Quality specifications were based on biological variation. Local reference intervals were reported from all laboratories. RESULTS Method differences that exceeded acceptable bias were found for all components except folate. Free T4 differences from the uncommonly used reference measurement procedure were large. Reference intervals differed between measurement procedures but also within 1 measurement procedure. The serum X material was commutable for all components and measurement procedures, whereas the EQA materials were noncommutable in 13 of 50 occasions (5 components, 5 methods, 2 EQA materials). CONCLUSIONS The bias between the measurement procedures was unacceptably large in 4/5 tested components. Traceability to reference materials as claimed by the manufacturers did not lead to acceptable harmonization. Adjustment of reference intervals in accordance with method differences and use of commutable EQA samples are not implemented commonly.

Dimensions of plane and solid angles and their units in the International System of Units (SI)

2020 ◽  
pp. 26-32
Author(s):  
M. I. Kalinin ◽  
L. K. Isaev ◽  
F. V. Bulygin
Keyword(s):  
Solid Angle ◽  
International System ◽  
International Committee ◽  
Plane Angle ◽  
Arc Length ◽  
Weights And Measures ◽  
International System Of Units ◽  
System Of Units ◽  
In Series ◽  
Solid Angles

The situation that has developed in the International System of Units (SI) as a result of adopting the recommendation of the International Committee of Weights and Measures (CIPM) in 1980, which proposed to consider plane and solid angles as dimensionless derived quantities, is analyzed. It is shown that the basis for such a solution was a misunderstanding of the mathematical formula relating the arc length of a circle with its radius and corresponding central angle, as well as of the expansions of trigonometric functions in series. From the analysis presented in the article, it follows that a plane angle does not depend on any of the SI quantities and should be assigned to the base quantities, and its unit, the radian, should be added to the base SI units. A solid angle, in this case, turns out to be a derived quantity of a plane angle. Its unit, the steradian, is a coherent derived unit equal to the square radian.

Harmonising EQA schemes the next frontier: challenging the status quo

2020 ◽  
Vol 58 (11) ◽  
pp. 1795-1797 ◽  
Author(s):  
Tony Badrick ◽  
Anne Stavelin
Keyword(s):  
External Quality Assessment ◽  
Reference Method ◽  
Laboratory Medicine ◽  
Status Quo ◽  
External Quality ◽  
Educational Support ◽  
Laboratory Results ◽  
The Status ◽  
Clinically Significant ◽  
Eqa Schemes

AbstractThere is a focus on standardisation and harmonisation of laboratory results to reduce the risk of misinterpretation of patient results assayed in different laboratories. External quality assessment (EQA) is critical to assess the need for harmonisation and to monitor the success of procedures to achieve harmonisation. However, EQA providers are being stretched to meet the needs of their participants with proven commutable material with reference method targets, a range of clinically significant levels of the materials, detailed and customised data analysis, and educational support. The path ahead for harmonisation of EQA schemes will require leadership from an organisation that has the support and confidence of EQA providers, like the European Organisation for External Qualily Assurance Providers in Laboratory Medicine.

scholarly journals A quantum ampere

2020 ◽  
Vol 87 (4) ◽  
pp. 258-265
Author(s):  
Luca Callegaro
Keyword(s):  
Electric Current ◽  
International System ◽  
International System Of Units ◽  
System Of Units ◽  
Elementary Charge ◽  
User Friendly

AbstractThe revision of the International System of Units (SI), implemented since 20 May 2019, has redefined the unit of electric current, the ampere ( A), linking it to a fixed value of the elementary charge. This paper discusses the new definition and the realisation of the electrical units by quantum electrical metrology standards, which every year become more and more accessible, reliable and user friendly.

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