Standardization of measurements of 25-Hydroxyvitamin D3 and D2

Figures & data

Figure 1. The development and implementation of evidence-based clinical guidelines depends on the comparability of tests performed in research and patient care. Adopted (and modified) from CP Price and RH Christenson (eds): [6].

Figure 2. Stevps to laboratory standardization.

Table I. Overview of the elements of an SI-reference measurement system, with indication of the related tasks and responsibilities.

Element	Organization	Task
SI-Unit	Conférence Générale des Poids et Mesures (CGPM)	Establishment of a coherent system of units (mol)
Component (analyte)	IFCC	Definition of the relevant component
Reference material	National Metrology Institutes; IRMM, NIST	Realization of SI units. Production and certification of reference material
Reference measurement procedure	Reference laboratory or other competent analytical laboratory	Development and validation of reference measurement procedures
Reference laboratory	No representative organization (“Networks”)	Application of the reference measurement procedures

Figure 3. Outline of the reference measurement system for serum/plasma 25(OH)D.

Table II. Recommendation for maximum imprecision (CV), bias and expanded uncertainty (U) of measurements and primary calibrators in a 25(OH)D reference measurement system [41].

Routine measurements	CV: 10 %	Bias: 5 %
Reference measurements	CV: 5 %	Bias: 1.7 %
Primary calibrators	U: 0.6 %

Figure 4. Procedure for standardization and performance certification.

Price CP, Christenson RH, editors. Evidence-Based Laboratory Medicine: Principles, Practice and Outcomes. 2nd ed. Washington DC: AACC Press; 2007. pp. 29–31

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