reference measurement procedures emphasis on …€¦ · · 2018-02-19institutes (irmm, nist)...
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Reference Measurement Procedures – Emphasis on performance
specifications and operating laboratories
Introduction
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The measurement paradigm
Routine assays claiming that they measure the
same measurand should give equivalent results
within clinically meaningful limits/agreed upon
performance specifications
Accomplishing this requires the establishment of
metrological traceability, ideally to the SI (also
called standardization)
Establishment of traceability
ISO 17511: 2003
In vitro diagnostic medical devices –
Measurement of quantities in biological samples –
Metrological traceability of values assigned to
calibrators and control materials (under revision)
to the highest metrological
standard available at a certain time for a
particular quantity subject to measurement
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Origin of the traceability concept
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Cali JP An idea whose time has come. Clin Chem 1973;19:
291-3.
Tietz NW A model for a comprehensive measurement system
in clinical chemistry. Clin Chem 1979; 25:833-9.
Precursor of the ISO 17511
reference measurement system/
metrological traceability chain
Reference measurement system
Traceability to the SI
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Gravimetry
Assay xyz
master procedure
Assay xyz
end user’s procedure
Primary calibrator
Product calibrator
Routine sample
Unit realizationCrystalline material of certified purity
Patient xyz
*** mmol/L
Reference method
Commutable working
calibrator
SI – Measurand (system/component/kind-of-
quantity)
Un
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Reference measurement system
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Metric anchor Meter Convention/General Conference on Weights and
Measures – SI
Amount of substance: mole (symbol mol)
Amount of substance concentration: mol/L
Reference measurement system
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.
Measurement anchor Measurand
Quantity ‘intended’ to be measured
To specify by 3 elements:
System/component or analyte/kind-of-quantity
Reference measurement system
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Material and analytical anchors
Reference materials1
• Primary calibrators (certified purity)
• Commutable secondary matrix-based calibrators
Trueness-based reference measurement procedures2
Reference measurement laboratories3
1ISO 15194:2009
In vitro diagnostic medical devices – Measurement of quantities in samples of
biological origin – Requirements for certified reference materials and the content of
supporting documentation.
2ISO 15193: 2009 In vitro diagnostic medical devices – Measurement of quantities in samples of biological origin – Requirements for content and presentation of reference measurement procedures.
3ISO 15195: 2003
Laboratory medicine – Requirements for reference measurement laboratories.
Reference measurement system
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Anchors Organization Responsibilities
Unit
(preferably: the SI)
International Committee
& International Bureau for
Weights and Measures
Establishment/
maintenance of a
coherent system of
units
Measurand
(system-component-
kind of quantity)
IFCC Definition of the relevant
component (analyte)
Reference materials
(RM’s)
National Metrology
Institutes (IRMM, NIST)
Realization of the SI:
production and
certification of RM’s
Reference
measurement
procedures (RMP’s)
Reference laboratories or
other competent
analytical laboratories
Development and
validation of RMP’s
Reference laboratories
Networks
Application of RMP’s
Reference measurement procedures
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Requirements that must be fulfilled
• Genuine/analytical characteristics
• Quality of performance
• Performed by competent laboratories
Trueness of measurement
Reference measurement procedures
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Requirements#
(i) Genuine/analytical characteristics
• Measurement principle
• Analytical validity
• Directly calibratable with a primary calibrator
• Potential to high specificity (matrix-insensitive) and
trueness of measurement
• Proof of full exploitation of this potential by
validation/documentation
Examples: IDMS, coulometry, gravimetry,
AAS, … #ISO 15193: 2009 In vitro diagnostic medical devices – Measurement of quantities in samples of biological origin – Requirements for content and presentation of reference measurement procedures.
Overarching control
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http://www.bipm.org/en/committees/jc/jctlm/
Database of reference materials &
reference measurement procedures
with ISO compliance
Joint Committee for Traceability
in Laboratory Medicine (JCTLM)
Pioneers in IDMS RMP’s
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Siekmann L et al.
IDMS method development
Zur gas-chromatographisch-massenspektrometrischen Bestimmung von Steroidhormonen in Körperflüssigkeiten unter Verwendung eines Multiple Ion Detectors (Fragmentographie). Z Anal Chem 1970;252:294-8.
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Björkhem I et al. Assay of cortisol with a
radioimmunoassay method
calibrated by isotope dilution
- mass spectrometry.
Scand J Clin Lab Invest
1983;43:433-7.
used in the RIA method
…
Pioneers in IDMS and commutability
Commutability – Assessment
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Property of a that indicates how well it mimics the characteristics of
in measurement procedures for a stated measurand
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Björkhem I et al. Assay of cortisol with a
radioimmunoassay method
calibrated by isotope dilution
- mass spectrometry.
Scand J Clin Lab Invest
1983;43:433-7.
used in the RIA method
… were replaced by
in which the concentration of cortisol
had been determined by the reference IDMS
method”.
Pioneers in IDMS and commutability
Reference measurement system
Traceability to the SI
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Gravimetry
Assay xyz
master procedure
Assay xyz
end user’s procedure
Primary calibrator
Product calibrator
Routine sample
Unit realizationCrystalline material of certified purity
Patient xyz
*** mmol/L
Reference method
Working calibrator:
panel of native samples
SI – Measurand (system/component/kind-of-
quantity)
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bilit
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University of Gent contributions
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ID-MS Reference Measurement Procedures
Substrates/Metabolites Steroid hormones &
vitamin metabolites
Cholesterol Cortisol
Creatinine Estradiol
Glucose Progesterone
Total triglycerides Total/Free Testosterone
Uric acid 25OH-Vitamin D2/D3
Peptides/Proteins Thyroid hormones
Human C-peptide Total/Free T4 & T3
Human insulin
HbA1c
University of Gent contributions
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Director of an ISO 17025 & 15195
accredited reference laboratory
Reference measurement procedures
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Requirements (continued)
(ii) Quality of performance
• Random, systematic and total error (n)
• Not fixed but commensurate with the intended use,
i.e., establishing/assessing measurement trueness
of hierarchically lower measurement procedures
Concepts defining tailor made
performance specifications
Proposals
Stöckl D, et al. Diskussionsvorschlag für ein einheitliches
Referenzmethodenkonzept auf der Grundlage der "Richtlinien der
Bundesärztekammer zur Qualitätssicherung in medizinischen
Laboratorien". Lab Med 1991;15:336-9.
Stöckl D, Reinauer H. Development of criteria for the evaluation of
reference method values. Scand J Clin Lab Invest Suppl 1993;212:16-8.
Stöckl D, Franzini C, Kratochvila J, Middle J, Ricos C, Siekmann L,
Thienpont LM. Analytical specifications of reference methods –
Compilation and critical discussion (from the members of the European
EQA-Organizers Working Group B). Eur J Clin Chem Clin Biochem
1996;34:319-37 [Review].
Thienpont LMR. Quality Specifications for Reference Methods. Scand J
Clin Lab Invest 1999;59:535-8.
Stöckl D, Sluss PM, Thienpont LM. Specifications for trueness and
precision of a reference measurement system for serum/plasma 25-
hydroxyvitamin D analysis. Clin Chim Acta 2009;408:8-13.
Performance specifications
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Performance specifications – Concepts
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For EQA: “Outcome-related” Fraction of the EQA limit resulting in a false
discrimination rate of 0.7%#
#Stöckl D et al. Eur J Clin Chem Clin Biochem 1996;34:319-37 [Review].
Analyte CV (%)# Bias (%)#
Chloride 1 0.5
Calcium 1.5 0.5
Creatinine 1.5 0.6
Thyroxine 2 0.9
Cortisol 2 1.4
#Together with specified n measurements
Performance specifications – Concepts
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For the complete RMS (25OHD) Start from desirable performance goals for
routine measurement procedures and cascade down#
#Stöckl D, Sluss PM, Thienpont LM. Specifications for trueness and precision
of a reference measurement system for serum/plasma 25-hydroxyvitamin D
analysis. Clin Chim Acta 2009;408:8-13.
Within-subject
variation (CVw = 8%)
CV: 4%
Bias: 2.6%
Reference interval
(CVg = 20%)
CV: 10%
Bias: 5%
Monitoring
Diagnosis
Monitoring
Diagnosis
Performance specifications – Concepts
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Reference performance goals
Cascade down from routine performance goals
Uncertainty of primary calibrators
Cascade down from reference bias goals
Model Routine Reference
Monitoring CV = 4%
Bias: 2.6%
CV: 2%
Bias 0.9%
U: 0.3%
Diagnosis CV: 10%
Bias: 5%
CV: 5%
Bias: 1.7%
U: 0.6%
CVref = 0.5 CVrou
Bref = 0.33 Brou
Urm = 0.33 Bref
Routine
measurements
CV: 10%
Bias: 5%
Reference
measurements
CV: 5%
Bias: 1.7%
Primary calibrators U: 0.6%
Performance specifications – Concepts
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Proposal for current “working specifications”
Hold the balance between “desirable” Q-goals - “state-
of-the-art” performance - certification capabilities
Select performance goals based on “diagnosis model”
(= maximum values)
Note: Stable imprecision and bias should be ~1/2 of the
limit in order to not exceed it!
Routine
measurements
CV: 10%
Bias: 5%
Reference
measurements
CV: 5%
Bias: 1.7%
Primary calibrators U: 0.6%
Performance specifications 25OHD RMS
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Vitamin D
Standardization
Program (VDSP)# #Sempos CT, Vesper HW , Phinney KW, Thienpont LM, Coates PM & The Vitamin D
Standardization Program (VDSP). Scand J Clin Lab Invest 2012; 72(Suppl 243): 32-40.
#Thienpont LM et al. Scand J Clin Lab Invest 2012; 72(Suppl 243): 41–49.
Requirements (continued)
(iii) Performed by competent laboratories
• Be accredited (ISO 15195/17025#)
• Use published reference measurement procedures
• Perform rigorous internal accuracy control with
SRM’s/CRM’s
• Participate in round robin trials for reference
laboratories
• Preferably work under network conditions
#ISO 15195:2003
Laboratory medicine – Requirements for reference measurement laboratories.
#ISO/IEC 17025:2017
General requirements for the competence of testing and calibration
laboratories.
Reference measurement procedures
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Overarching control
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http://www.bipm.org/en/committees/jc/jctlm/
Database of reference measurement
services with ISO compliance
Joint Committee for Traceability
in Laboratory Medicine (JCTLM)
JCTLM database
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http://www.bipm.org
JCTLM-Newsletter-2017#
#For 80 different analytes in 9 categories: 293 CRM’s – 184 RMP’s – 161 reference
measurement services by 17 reference laboratories
Future of reference laboratories
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Bright? Regulatory environment: Directive & ISO
Traceability of IVD assays
EQA/PT emphasis on traceability
JCTLM
…
Viability of the “lonely-rider” academic
reference laboratory is a real challenge
Money, money, money
Future of reference laboratories
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Future of reference laboratories
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Willingness to standardize!
R. S. Yalow and S. A. Berson Assay of Plasma Insulin in Human Subjects by
Immunological Methods. Nature 1959;184:1648-1649.
The Nobel Prize in Physiology and Medicine 1977,
Rosalyn Yalow "for the development of
radioimmunoassays of peptide hormones".
Insulin measurement – Still NOT standardized
Future of reference laboratories
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The “lonely-rider” academic reference laboratory
Future of reference laboratories
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Embedded in a big organization
• EQA/PT organization
• Metrological institute (NIM’s)
• NIST, IRMM, CDC
Future of reference laboratories
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Leadership in a certain domain (e.g.,
endocrinology, TDM)
• Not for a single analyte but groups of analytes, e.g.,
− Steroid hormones
− Thyroid hormones
− Therapeutics
• Get all IVD manufacturers on board, cf., IFCC projects
PATH Initiative