SIST EN ISO 17511:2003

SLOVENSKI STANDARD
01-november-2003
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In vitro diagnostic medical devices - Measurement of quantities in biological samples -
Metrological traceability of values assigned to calibrators and control materials (ISO
17511:2003)
In-vitro-Diagnostika - Messung von Größen in Proben biologischen Ursprungs -
Metrologische Rückführbarkeit von Werten, die Kalibriermaterialien und
Kontrollmaterialien zugeordnet sind (ISO 17511:2003)
Dispositifs médicaux de diagnostic in vitro - Mesurage des grandeurs dans des
échantillons d'origine biologique - Traçabilité métrologique des valeurs attribuées aux
agents d'étalonnage et aux matériaux de contrôle (ISO 17511:2003)
Ta slovenski standard je istoveten z: EN ISO 17511:2003
ICS:
11.100.10 'LDJQRVWLþQLSUHVNXVQL In vitro diagnostic test
VLVWHPLLQYLWUR systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 17511
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2003
ICS 07.100.10
English version
In vitro diagnostic medical devices - Measurement of quantities
in biological samples - Metrological traceability of values
assigned to calibrators and control materials (ISO 17511:2003)
Dispositifs médicaux de diagnostic in vitro - Mesurage des In-vitro-Diagnostika - Messung von Größen in Proben
grandeurs dans des échantillons d'origine biologique - biologischen Ursprungs - Metrologische Rückführbarkeit
Traçabilité métrologique des valeurs attribuées aux agents von Werten, die Kalibriermaterialien und Kontrollmaterialien
d'étalonnage et aux matériaux de contrôle (ISO zugeordnet sind (ISO 17511:2003)
17511:2003)
This European Standard was approved by CEN on 11 March 2003.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2003 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17511:2003 E
worldwide for CEN national Members.

Contents
page
Foreword.3
Introduction .4
1 Scope .6
2 Normative references .6
3 Terms and definitions.6
4 Metrological traceability chain and calibration hierarchy .12
4.1 Principles.12
4.2 Structure and nomenclature.13
4.3 Considerations in establishing metrological traceability.17
4.4 Functions of reference materials .18
5 Calibration transfer protocols .18
5.1 Availability and structure.18
5.2 Cases with primary reference measurement procedure and primary calibrator(s) giving
metrological traceability to SI.19
5.3 Cases with international conventional reference measurement procedure (which is not
primary) and international conventional calibrator(s) without metrological traceability to SI.20
5.4 Cases with international conventional reference measurement procedure (which is not
primary) but no international conventional calibrator and without metrological traceability to
SI.21
5.5 Cases with international conventional calibrator (which is not primary) but no international
conventional reference measurement procedure and without metrological traceability to SI .22
5.6 Cases with manufacturer's selected measurement procedure but neither international
conventional reference measurement procedure nor international conventional calibrator and
without metrological traceability to SI.23
5.7 Trueness control materials.24
6 Expression of uncertainty of measurement.24
7 Validation of metrologically traceable calibration.25
8 Information on metrological traceability to be given in the instructions for use of an in vitro
diagnostic medical device .26
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or other
provisions of EU Directives .27
Bibliography .28
Foreword
This document (EN ISO 17511:2003) has been prepared by Technical Committee CEN/TC 140 "In vitro diagnostic
medical devices", the secretariat of which is held by DIN, in collaboration with Technical Committee ISO/TC 212
"Clinical laboratory testing and in vitro diagnostic test systems".
This European Standard EN ISO 17511:2003 including the Amendment shall be given the status of a national
standard, either by publication of an identical text or by endorsement, at the latest by February 2004, and
conflicting national standards shall be withdrawn at the latest by February 2004.
This document has been prepared under a mandate given to CEN by the European Commission and the European
Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative annex ZA, which is an integral part of this document.
The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), the European Confederation of
Laboratory Medicine (ECLM), and the European Diagnostic Manufacturers Association (EDMA) have contributed to
its preparation.
This standard includes a Bibliography.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal,
Slovakia, Spain, Sweden, Switzerland and the United Kingdom.
Introduction
For measurements of quantities in laboratory medicine, it is essential that the quantity is adequately defined and
that the results reported to the physicians or other health care personel and patients are adequately accurate (true
and precise) to allow correct medical interpretation and comparability over time and space.
NOTE In this European Standard the concept "accuracy of measurement" (see 3.1) is related to both "trueness of
measurement" (see 3.33) and "precision of measurement" (see 3.23) whereas the Directive 98/79/EC on in vitro diagnostic
medical devices uses the term ‘’accuracy'’ instead of ‘'trueness’'.
To allow 'correct medical interpretation' involves more than the metrological (analytical) aspects of the traceability
chain. As the measurement results are eventually used by the physician for the benefit of the patients, the
physician should gather information on a number of other aspects, such as knowledge about the pre- and post-
analytical phase, the diagnostic sensitivity and specificity, and relevant reference interval(s). The present European
Standard deals only with the analytical aspects of measurements in Laboratory Medicine (see also 1 e)).
The measurement of quantities in biological samples requires reference measurement systems including:
- the definition of the analyte in the biological sample with regard to the intended clinical use of the measurement
results;
- a reference measurement procedure for the selected quantity in human samples;
- suitable reference materials for the selected quantity, e.g. primary calibrators and secondary matrix-based
calibrators that are commutable.
The trueness of measurement of a value assigned to a defined quantity of a calibrator or trueness control material,
depends on the metrological traceability of the value through an unbroken chain of alternating measurement
procedures and measurement standards (calibrators), usually having successively decreasing uncertainties of
measurement (see Figure 1). The uncertainty of the value assigned to a given calibrator or trueness control
material depends on the stated metrological traceability chain and the combined uncertainties of its links.
The ideal end-point of a metrological traceability chain is the definition of the relevant unit of the International
System of Units (SI), but the selection of steps and the level at which metrological traceability for a given value
stops, depend on the availability of higher order measurement procedures and calibrators. In many cases, at
present, there is no metrological traceability above the manufacturer's selected measurement procedure or the
manufacturer's working calibrator. In such cases, trueness is referred to that level of the calibration hierarchy until
an internationally agreed reference measurement procedure and/or calibrator becomes available.
The objective of a chosen metrologically traceable calibration is to transfer the degree of trueness of a reference
material, and/or reference measurement procedure, to a procedure that is of a lower metrological order, e.g. a
routine procedure. Metrological traceability of calibration requires that the reference and routine measurement
procedures measure the same measurable quantity with an analyte of the same pertinent characteristics.
In this context, it is important to recognize that different procedures purporting to measure the same quantity may in
fact give different results when applied to a particular sample or reference material. This may arise, for example,
when two or more immunoprocedures purporting to measure the concentration of a hormone such as thyrotropin
(thyroid stimulating hormone, TSH) are applied to a reference material of the hormone, because the respective
reagents recognize and react to different extents with various epitopes in the material, thus leading to results for
different although related quantities.
Laboratory medicine routinely provides results for 400 to 700 types of quantity. For most of these, the metrological
traceability of the assigned value for a product calibrator stops after only one metrologically higher step consisting
of a (reference) measurement procedure, or after two steps consisting of a measurement procedure and a
(reference) calibrator. The reason is that many of such quantities are related to mixtures of molecular species with
clinically relevant properties in common, but with different structures and molecular masses in varying proportions,
e.g. glycoproteins.
Depending on the possibility of metrological traceability to SI and on the availability of various metrological levels of
measurement procedures and calibrators, the following five typical upper ends of the metrological traceability chain
can be identified.
a) Quantities for which results of measurements are metrologically traceable to SI.
A primary reference measurement procedure and one or more (certified) primary reference materials (used as
calibrators) are available. These levels exist for approximately 25 to 30 types of quantity having well defined
components, e.g. some electrolytes, metabolites, steroid hormones, and some thyroid hormones. These types
of quantity cover a large proportion of the routine results provided by medical laboratories (see 4.2.2, 5.2,
Figures 1 and 2).
b) Quantities for which results of measurements are not metrologically traceable to SI.
1) An international conventional reference measurement procedure (see 3.12) (which cannot be called a
primary reference measurement procedure) and one or more international conventional calibration materials
(see 3.11) with values assigned by that procedure are available. These conditions apply for quantities with
components such as HbA (see 5.3 and Figure 3).
1c
2) An international conventional reference measurement procedure is available but no international
conventional calibration materials. These conditions apply for about 30 types of quantity with components such
as haemostatic factors (see 5.4 and Figure 4).
3) One or more international conventional calibration materials (used as calibrators) with a protocol for value
assignment are available, but no international conventional reference measurement procedure. These
conditions apply for over 300 types of quantity, e.g., for quantities referred to World Health Organization's
International Standards, such as protein hormones, some antibodies, and tumour markers (see 5.5 and
Figure 5).
4) Neither reference measurement procedure nor reference materials for calibration are available. The
manufacturer can establish 'in-house' measurement procedure(s) and calibrator(s) to support value
assignment to his product calibrator. These conditions apply for about 300 types of quantity with components
such as tumour markers and antibodies (see 5.6 and Figure 6).
The principles of the respective transfer protocols (calibration hierarchies) are presented, given the provisions of
the European Standards EN 12286 on presentation of reference measurement procedures and EN 12287 on the
description of reference materials.
It is the aim of metrology in laboratory medicine to improve metrological traceability for results of a type of quantity
from the conditions described under b2), b3), and b4) to those of b1) by providing the missing reference
measurement procedures and reference materials, based on international consensus.
The special problems of metrological traceability for values of catalytic concentration of enzymes are considered in
prEN ISO 18153.
1 Scope
This European Standard specifies how to assure the metrological traceability of values assigned to calibrators and
control materials intended to establish or verify trueness of measurement. The calibrators and control materials are
those provided by the manufacturers as part of, or to be used together with, in vitro diagnostic medical devices.
External quality assessment (survey) samples, with proven commutability, whose values have been assigned by
means of internationally agreed reference measurement systems or internationally agreed conventional reference
measurement systems fall within the scope of this European Standard.
This European Standard is not applicable to:
a) control materials that do not have an assigned value and are used only for assessing the precision of a
measurement procedure, either its repeatability or reproducibility (precision control materials);
b) control materials intended for intralaboratory quality control purposes and supplied with intervals of suggested
acceptable values, each interval obtained by interlaboratory consensus with respect to one specified
measurement procedure, and with limiting values that are not metrologically traceable;
c) correlation between results of two measurement procedures at the same metrological level, purporting to
measure the same quantity, because such 'horizontal' correlation does not provide metrological traceability;
d) calibration derived from correlation between the results of two measurement procedures at different
metrological levels, but with quantities having analytes of different characteristics;
e) metrological traceability of routine results to the product calibrator and their relations to any medical
discrimination limit;
f) properties involving nominal scales, i.e. where no magnitude is involved (e.g. identification of blood cells).
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text, and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
EN 375:2001, Information supplied by the manufacturer with in vitro diagnostic reagents for professional use.
) )
1 2
International Vocabulary of Basic and General Terms in Metrology, 2nd edition, ISO, Geneva, 1993.
ISO Guide 35:1989, Certification of reference materials - General and statistical principles.
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply:
3.1
accuracy of measurement
closeness of the agreement between the result of a measurement and a true value of the measurand

)
This monograph has been prepared simultaneously in English and French by a joint working group consisting of experts appointed by: BIPM
(International Bureau of Weights and Measures), IEC (International Electrotechnical Commission), IFCC (International Federation of Clinical
Chemistry and Laboratory Medicine), ISO (International Organization for Standardization), IUPAC (International Union of Pure and Applied
Chemistry), IUPAP (International Union of Pure and Applied Physics), OIML (International Organization of Legal Metrology)
)
The abbreviation VIM:1993 is used in this standard
[VIM:1993, 3.5]
NOTE 1 Accuracy of measurement is related to both trueness of measurement and precision of measurement.
NOTE 2 Accuracy cannot be given a numerical value in terms of the measurand, only descriptions such as 'sufficient' or
'insufficient' for a stated purpose.
NOTE 3 An estimator of an inverse measure of accuracy is "deviation", defined as 'value minus a conventional true value'.
NOTE 4 ISO 3534-1, instead of "a true value" in the definition above, uses the concept "the accepted reference value", which
can be a theoretical (true), assigned, consensus, or procedure-defined value.
NOTE 5 In this standard the concept "accuracy of measurement" is related to both "trueness of measurement" (see 3.33)
and "precision of measurement" (see 3.23) whereas the Directive 98/79/EC on in vitro diagnostic medical devices uses the term
'accuracy' instead of 'trueness'.
3.2
analyte
component represented in the name of a measurable quantity
EXAMPLE In the type of quantity "mass of protein in 24-hour urine", "protein" is the analyte. In "amount of substance of
glucose in plasma", "glucose" is the analyte. In both cases the long phrase represents the measurand (see 3.17).
3.3
analytical specificity
ability of a measurement procedure to measure solely the measurand
3.4
bias of measurements
difference between the expectation of the results of measurement and a true value of the measurand
NOTE An estimator is the "statistical sample bias of measurements" which is the 'average minus its reference value'.
3.5
calibration
set of operations that establish, under specified conditions, the relationship between values of quantities indicated
by a measuring instrument or measuring system, or values represented by a material measure or a reference
material, and the corresponding values realized by standards
[VIM:1993, 6.11]
NOTE The term ''standard'' here refers to "measurement standard" (see 3.19), not a written standard.
3.6
calibration transfer protocol
transfer protocol
detailed description for assigning a value of a quantity to a reference material using a specified sequence of
measurement procedures calibrated by higher-order reference materials for the same type of quantity
3.7
calibrator
calibration material
reference material whose value is used for the independent variable in a calibration function
3.8
certified reference material
CRM
reference material, accompanied by a certificate, one or more of whose property values are certified by a
procedure which establishes metrological traceability to an accurate realization of the unit in which the property
values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of
confidence
[slightly adapted from VIM:1993, 6.14]
3.9
commutability of a material
closeness of agreement between the mathematical relationship of the measurement results obtained by two
measurement procedures for a stated quantity in a given material, and the mathematical relationship obtained for
the quantity in routine samples
3.10
influence quantity
quantity that is not the measurand but that affects the result of the measurement
[VIM:1993, 2.7]
3.11
international conventional calibrator
international conventional calibration material
calibrator whose value of a quantity is not metrologically traceable to the SI but is assigned by international
agreement
NOTE The quantity is defined with respect to the intended clinical application.
3.12
international conventional reference measurement procedure
measurement procedure yielding values that are not metrologically traceable to the SI but which by international
agreement are used as reference values for a defined quantity
NOTE The quantity is defined with respect to the intended clinical application.
3.13
international measurement standard
international standard
standard recognized by an international agreement to serve internationally as the basis for assigning values to
other standards of the quantity concerned
[VIM:1993, 6.2]
3.14
matrix of a material system
matrix
totality of components of a material system except the analyte
[EN 12287:1999, 3.3]
3.15
matrix effect
influence of a property of the sample, other than the measurand, on the measurement of the measurand according
to a specified measurement procedure and thereby on its measured value
NOTE 1 A specified cause of a matrix effect is an influence quantity.
NOTE 2 The term 'matrix effect' is sometimes erroneously used for the lack of commutability due to a denatured analyte or
an added non-genuine component ('surrogate analyte') meant to simulate the analyte.
3.16
measurable quantity
quantity
attribute of a phenomenon, body or substance that may be distinguished qualitatively and determined quantitatively
[VIM:1993, 1.1]
NOTE 1 Properties that are expressed on a nominal scale are not measurable quantities.
NOTE 2 "Measurable quantity" is not to be confused with "analyte", see 3.2.
3.17
measurand
particular quantity subject to measurement
[VIM:1993, 2.6]
NOTE See 3.2, Example.
3.18
measurement procedure
set of operations, described specifically, used in the performance of particular measurements according to a given
method
[VIM:1993, 2.5]
3.19
measurement standard
material measure, measuring instrument, reference material or measuring system intended to define, realize,
conserve or reproduce a unit or one or more values of a quantity to serve as a reference
[VIM:1993, 6.1]
NOTE 1 A given measurement standard with an assigned value for one quantity can sometimes serve as a reference
material for measurement procedures yielding values for more than one type of quantity. (For example, a reference material for
cholesterol also serving for cholesterol esters that are measured after hydrolysis as cholesterol).
NOTE 2 The term 'standard' is used with two meanings: "measurement standard" and "written standard". The full terms
should be used when doubt can arise.
3.20
method of measurement
logical sequence of operations, described generically, used in the performance of measurements
[VIM:1993, 2.4]
NOTE A method of measurement, due to its generalized description, does not have numerically specified performance
characteristics. A given method can be the basis of one or more measurement procedures, each with inherent numerical values
for its performance characteristics.
3.21
metrological traceability
property of the result of a measurement or the value of a standard whereby it can be related to stated references,
usually national or international standards, through an unbroken chain of comparisons all having stated
uncertainties
[VIM:1993, 6.10]
NOTE 1 Each comparison is effected by a (reference) measurement procedure defined in a calibration transfer protocol.
NOTE 2 There are several types of traceability. Therefore the term 'metrological traceability' is used in the present text.
3.22
metrology
science of measurement
NOTE Metrology includes all aspects both theoretical and practical with reference to measurements, whatever their
uncertainty, and in whatever fields of science or technology they occur.
[VIM:1993, 2.2]
3.23
precision of measurement
closeness of agreement between independent results of measurements obtained under stipulated conditions
[ISO 3534-1:1993, 3.14]
NOTE 1 Precision of measurement cannot be given a numerical value in terms of the measurand, only descriptions such as
'sufficient' or 'insufficient' for a stated purpose.
NOTE 2 The degree of precision is usually expressed numerically by the statistical measures of imprecision of
measurements, such as standard deviation and coefficient of variation, that are inversely related to precision.
NOTE 3 "Precision" of a given measurement procedure is subdivided according to the specified precision conditions.
"Repeatability" relates to essentially unchanged conditions and is often termed "withinserial" or "within-run precision".
"Reproducibility" relates to changes in conditions, e.g. time, different laboratories, operators, and measuring systems (including
different calibrations and reagent batches).
3.24
primary reference material
reference material having the highest metrological qualities and whose value is determined by means of a primary
reference measurement procedure
NOTE 1 The concept "primary calibrator" is subordinate to "calibrator" (see 3.7) and to "primary reference material".
NOTE 2 See 3.26, Note.
3.25
primary reference measurement procedure
reference measurement procedure having the highest metrological qualities, whose operation can be completely
described and understood, for which a complete uncertainty statement can be written down in terms of SI units,
and where results are, therefore, accepted without reference to a measurement standard of the quantity being
measured
NOTE The Consultative Committee on Amount of Substance (CCQM) uses the term "primary method of measurement",
but the term "primary reference measurement procedure" in the present context is in conformity with VIM (see 3.19 with Note).
The term "definitive method'" was omitted in VIM, but is sometimes used for a thoroughly investigated and evaluated reference
measurement procedure (see 3.29) of high accuracy.
3.26
primary measurement standard
primary standard
standard that is designated or widely acknowledged as having the highest metrological qualities and whose value
is accepted without reference to other standards of the same quantity
[VIM:1993, 6.4]
NOTE For reference materials, the value can be obtained by applying a primary reference measurement procedure.
3.27
product calibrator
calibrator intended for use with the manufacturer's final product
3.28
reference material
RM
material or substance one or more of whose property values are sufficiently homogeneous and well established to
be used for the calibration of an apparatus, the assessment of a measurement procedure, or for assigning values
to materials
NOTE 1 Adapted from VIM:1993, 6.13.
NOTE 2 The adjective 'homogeneous' refers to the physical homogeneity between macroscopic parts of the material, not to
any microheterogeneity between molecules of the analyte.
3.29
reference measurement procedure
thoroughly investigated measurement procedure shown to yield values having an uncertainty of measurement
commensurate with its intended use, especially in assessing the trueness of other measurement procedures for the
same quantity and in characterizing reference materials
[EN 12286:1998, 3.7]
3.30
secondary measurement standard
secondary standard
standard whose value is assigned by comparison with a primary standard of the same quantity
[VIM:1993, 6.5]
3.31
true value of a quantity
true value
value consistent with the definition of a given particular quantity
[VIM:1993, 1.19]
NOTE 1 This is a value that would be obtained by a perfect measurement.
NOTE 2 True values are by nature indeterminate.
NOTE 3 The indefinite article "a", rather than the definite article "the", is used in conjunction with "true value" because there
may be many values consistent with the definition of a given particular quantity.
NOTE 4 The 'definition of a given particular quantity' may have to include the measurement procedure applied. Therefore, a
true value may depend on a specified measurement procedure.
3.32
trueness control material
reference material that is used to assess the bias of measurement of a measuring system
3.33
trueness of measurement
closeness of agreement between the average value obtained from a large series of results of measurements and a
true value
NOTE 1 Definition adapted from ISO 3534-1:1993, 3.12 that has '.test results and an accepted reference value' , which can
be a theoretical (true), assigned, consensus, or procedure-defined value.
NOTE 2 Concerning the phrase 'a true value', see 3.31, Note 2.
NOTE 3 Trueness of measurement cannot be given a numerical value in terms of the measurand, only ordinal values (e.g.
sufficient, insufficient).
NOTE 4 The degree of trueness is usually expressed numerically by the statistical measure bias that is inversely related to
trueness and is the difference between the expectation of the results of measurement and a true value of the measurand.
3.34
uncertainty of measurement
parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could
reasonably be attributed to the measurand
[VIM:1993, 3.9]
NOTE 1 The parameter can be, for example, a standard deviation (or a given multiple of it), or the half-width of an interval
having a stated level of confidence.
NOTE 2 The components of uncertainty are evaluated experimentally from statistical distributions (Type A) or evaluated from
assumed probability distributions based on experience or other information (Type B) (see [10]). All components are expressed
as standard uncertainties that are combined into one final expression.
3.35
validation
confirmation, through the provision of objective evidence that the requirements for a specific intended use or
application have been fulfilled
[EN ISO 9000:2000, 3.8.5]
3.36
verification
confirmation, through the provision of objective evidence, that specified requirements have been fulfilled
[EN ISO 9000:2000, 3.8.4]
3.37
working measurement standard
working standard
standard that is used routinely to calibrate or check material measures, measuring instruments or reference
materials
[VIM:1993, 6.7]
4 Metrological traceability chain and calibration hierarchy
4.1 Principles
4.1.1 Before a metrological traceability chain is established, the measurable quantity (measurand) shall be
defined with reference to the intended use of the result in medical decisions. The details of this definition shall
comprise as appropriate:
a) intended use of the quantity with regard to a particular medical decision (e.g. choriogonadotropin (hCG) in
plasma as a tumour marker or for the detection and monitoring of pregnancy);
b) biological system (e.g. human serum) and any pertinent component (e.g. sodium ion) to be characterized by
the quantity as defined by relevant international scientific organizations (e.g. IFCC, ICSH), and/or the
manufacturer;
c) kind-of-quantity (e.g. amount-of-substance concentration) defined by the General Conference on Weights and
Measures (CGPM), ISO, WHO, international scientific organizations, and/or the manufacturer;
d) unit of measurement (e.g. mmol/l), if any, defined by CGPM, WHO, international scientific organizations,
and/or the manufacturer.
4.1.2 The objective of metrological traceability shall be to enable the results obtained by the calibrated routine
procedure to be expressed in terms of the values obtained at the highest available level of the calibration hierarchy.
The metrological traceability chain shall be established before initiating the final measurement, and shall be
described by a calibration hierarchy descending in the opposite direction, that is from the metrologically highest
reference to the result of the end-user (see Figure 1).
4.1.3 Each level in the calibration hierarchy shall be a measurement procedure or a measurement standard, the
latter being a measuring system or a reference material functioning as a calibrator.
4.1.4 A given measurement standard with its assigned value shall serve to calibrate the measurement standard
at the next lower level by way of a measurement procedure as specified in a transfer protocol.
NOTE When the calibration function is based on more than one calibrator, such calibrators can be separate in origin or be
produced from one measurement standard, e.g. by dilution.
4.1.5 The value assigned to a measurement standard at a given level shall be associated with an uncertainty of
measurement that shall include inherited consecutive uncertainty contributions from measurement standards and
measurement procedures at all higher levels of the calibration hierarchy.
NOTE The chosen measure of uncertainty preferably should be estimated according to the GUM (see clause 6).
4.1.6 To ensure the validity of a metrological traceability chain, the quantity shall be the same at all levels. The
analytical specificities of the described routine procedure and metrologically higher reference measurement
procedures as well as the stability and commutability of the calibrators shall be known or investigated. The
outcome shall be described in the manufacturer's technical documentation.
4.1.7 The responsibility of the manufacturer for describing the metrological traceability chain shall start at the
value of the manufacturer's product calibrator and end at the metrologically highest reference used by the
manufacturer. The uncertainty of this reference shall include any further upwards contributions to uncertainty.
4.2 Structure and nomenclature
4.2.1 As the structure of an actual metrological traceability chain depends on the metrological possibilities, any
description of the elements of the chain shall include or refer to definitions of terms and statements of the
metrological properties of measuring systems and reference materials involved.
NOTE 1 The series of measurement standards defined in VIM is based on the needs of calibration hierarchies for quantities
in physics, such as a length, a time, a temperature, a pressure, an electrical potential difference (voltage), a volume, and an
absorbance, and comprises
- primary measurement standard,
- secondary measurement standard,
- reference measurement standard,
- working measurement standard.
NOTE 2 For practical purposes - especially for quantities in chemistry - there should be a distinction between the elements in
the calibration hierarchy that are measuring systems, described in and operated according to a measurement procedure, and
those that are used for calibration of the measuring systems. The latter type is called calibration material or calibrator. In
chemical measurement the concept "reference material" includes "calibration material" and "trueness control material".
4.2.2 In a given calibration hierarchy providing metrological traceability to SI, the following concepts shall be
identified as appropriate (see Figure 1), see also 4.2.3 and 4.2.4.
a) SI unit of measurement, whether base or derived, to which metrological traceability preferably shall refer, for
-3
example mole, kilogram, mole per cubic metre (= millimole per litre), gram per kilogram (= 10 ).
b) Primary reference measurement procedure shall be based on a principle of measurement proved to be
analytically specific, providing metrological traceability to an SI unit of measurement without reference to a
calibrator for the same quantity, and having a low uncertainty of measurement.
NOTE 1 The International Committee on Weights and Measures (CIPM) in 1994 formed a Consultative Committee on
Amount of Substance (CCQM), which provisionally identified the following potential principles of measurement for primary
reference measurement procedures: isotope dilution-mass spectrometry, coulometry, gravimetry, titrimetry, freezing-point
depression measuremet for osmolality determination.
NOTE 2 A primary reference measurement procedure is usually endorsed by an international or national metrology institute
or by an international scientific body. National primary reference measurement procedures should not be developed. The
measurements preferably should be performed by a metrology institute or a laboratory accredited by a recognized accrediting
body as a calibration laboratory for that measurement procedure.
NOTE 3 More than one primary reference measurement procedure can exist at a given time for assigning values of
quantities of a given kind to primary calibrators. (The values obtained by two such procedures for a given measurand should not
be significantly different within a stated uncertainty at a certain level of confidence).
c) Primary calibrator that is an embodiment of the unit of measurement with the smallest achievable uncertainty
of measurement. The primary calibrator shall have its value assigned either directly by a primary reference
measurement procedure or indirectly by determining the impurities of the material by appropriate analytical
methods. The material usually is highly purified containing a physico-chemically well-defined analyte,
examined for stability, compositional integrity, and accompanied by a certificate (certified reference material,
CRM).
NOTE 4 The certification of a primary calibrator usually occurs in laboratories having the highest metrological expertise, such
as an international or national metrology institute.
d) Secondary reference measurement procedure shall describe a measuring system which is calibrated by one or
more primary calibrators.
NOTE 5 A secondary reference measurement procedure can be established in national metrology institutes or in reference
measurement laboratories accredited for that measurement procedure by a recognized accrediting body.
NOTE 6 A secondary reference measurement procedure can be based on a principle of measurement different from that of a
primary procedure.
e) Secondary calibrator shall have its value assigned according to one or more secondary reference
measurement procedures and is usually accompanied by a certificate.
NOTE 7 A secondary calibrator usually disseminates a unit of measurement from a national metrology institute to accredited
calibration laboratories and the manufacturer's calibration centre.
NOTE 8 A secondary calibrator can be, e.g., a material with a matrix resembling those of the samples of human origin to be
measured by the end-users' routine measurement procedures.
f) Manufacturer's selected measurement procedure shall define a measuring system which is calibrated by one
or more primary or secondary calibrators when available.
NOTE 9 A manufacturer's selected measurement procedure can be a secondary reference measurement procedure (see
4.2.2.d)).
g) Manufacturer's working calibrator shall have its value assigned according to one or more of the manufacturer's
selected measurement procedures. This calibrator is sometimes called "manufacturer's master calibrator" (or
"in-house calibrator"). The calibration material shall have demonstrated commutability as regards the
manufacturer's selected measurement procedure and the procedure to be calibrated.
NOTE 10 A manufacturer's working calibrator can be, e.g., a material with a matrix resembling those of the samples of human
origin to be measured by the end-users' routine measurement procedures.
h) Manufacturer's standing measurement procedure shall define a measurement procedure prescribing
calibration by one or more of the manufacturer's working calibrators or higher types of calibrator and is
validated for analytical specificity.
NOTE 11 The manufacturer's standing measurement procedure can be based on the same principle and method of
measurement as the routine measurement procedure, but should have a lower uncertainty of measurement obtained through,
e.g., a larger number of replicates and a stricter control system.
i) Manufacturer's product calibrator shall have its value assigned according to the manufacturer's standing
measurement procedure and is intended for calibration of the end-user's routine measurement procedure.
NOTE 12 A manufacturer's product calibrator can be, e.g., a material with a matrix resembling those of the samples of human
origin to be measured by the end-users' ro
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