1. Senior Lecturer in Pathology
Traceability of Results via Medical Reference Materials World Accreditation Day 2015 Technical Seminar
Dr ID Siriwardhana
Senior Lecturer in Pathology
Faculty of Medicine
University of Ruhuna
Galle

2. Overview What is metrological traceability?
Is it important to ensure traceability of results?
Who is responsible?
What are reference materials and reference methods?
Are there analytes without reference materials?

3. Metrology Definition – science of measurement
Measurements are comparisons against known standards

4. Metrological Traceability
Metrological Traceability “ property of a measurement result whereby the result can be related to a stated reference, through a documented unbroken chain of calibrations (comparisons),each contributing to the measurement uncertainty.”
International Vocabulary of Basic and General Terms in Metrology (VIM)

5. Metrological Traceability
Key Features
It is a property of a measurement result
The results are obtained through a series of comparisons to a reference standard
All comparison steps documented
Measurement uncertainty (MU)stated for each comparison step
Preferably results traceable to an SI unit

6. What is the significance of traceability?
Link measurement results of a patient sample to a commonly accepted reference (certified reference material or reference measurement procedure)
Renders measurement results comparable across different
methods and systems
locations
times

7. ISO 15189:2012
Metrological traceability shall be to a reference material or reference procedure of higher metrological order available.”
“documentation of calibration traceability to a higher order reference material or reference procedure may be provided by an examination system manufacturer.”

8. What are Reference Materials?
Primary Reference Materials
Used with a primary reference measurement procedure
To produce primary calibrators
Primary Calibrators
Used to calibrate secondary reference measurement procedure
To produce secondary calibrators
Secondary Calibrators
Used in manufacturer’s method
To produce master calibrators
Prepared using gravimetry
Primary calibrators are aqueous solutuions

9. Traceability Chain for Serum Calcium
SRM 915b (NIST) Mass Fraction of CaCO3
Gravimetry
SRM 3109a
Aqueous CaCO3
ID-TIMS
SRM 909b
(human serum)
Atomic absorption spectrometry
Master calibrator (Ca in mmo/L)

10. Do all analytes have primary and secondary Calibrators?No
Reason: most analytes are yet inadequately defined for
Physico-chemical characteristics
Molecular weights
Alternative: International conventional calibrators; Eg. hormones
Produced by international conventional reference measurement procedures

11. Lowest Order Metrological Traceability
No international reference measurement procedure or calibrator
Only a manufacturer’s method and calibrators
Eg. Tumour markers like CA 19-9

12. Information about Reference Materials
Joint Committee for Traceability in Laboratory Medicine (JCTLM)
National Institute of science and Technology (NIST)
Institute for Reference Materials and Measurements (IRMM)
WHO Expert Committee on Biological Standardization (WHO-ECBS)
International Federation for Clinical Chemistry and Laboratory Medicine (IFCC)
International Council for Standardization in Haematology (ICSH)