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

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?

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

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)

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

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

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.”

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

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)

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

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

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)