Traceability and Uncertainty of Measurement for …

1 QUALITY MANAGEMENT PROGRAM laboratory SERVICES (QMP LS) Ontario laboratory Accreditation Division (OLA) Traceability and Uncertainty of Measurement for Medical Laboratories Quality Management Program laboratory Services (QMP LS) April 2009, Version 1 Dr. Godfrey Moses and Linda Crawford Ontario laboratory Accreditation Division Suite 1510 250 Bloor Street East Toronto, ON Canada M6N 1Y9 Phone Fax Traceability and Uncertainty of Measurement for Medical Laboratories2009-04-14 Page 1 of 11 2009 Quality Management Program laboratory Services. All Ontario laboratory Accreditation program documents are the sole property and copyright of the Quality Management Program laboratory Services, ALL RIGHTS RESERVED.

2 No part of the material protected by this copyright may be reproduced without written permission from QMP LS. The logos and/or symbols used are the property of QMP LS or other third parties. You are not permitted to use these logos and/or symbols without written permission from QMP LS or such third party that may own the logos and/or symbols. Traceability and Uncertainty of Measurement for Medical Laboratories TABLE OF CONTENTS 2 2 3 3 3 OLA 3 Uncertainty OF 4 4 4 OLA 4 HOW TO DETERMINE/CALCULATE ESTIMATES OF Uncertainty OF Measurement IN THE MEDICAL DETERMINING ESTIMATES OF Uncertainty OF Measurement BY THE TOP-DOWN APPROACH USING INTRA- AND INTER- laboratory 5 ESTIMATES OF Uncertainty OF Measurement FOR SOME COMMON MEDICAL laboratory 7 A.

3 PLASMA OR SERUM GLUCOSE (FASTING PLASMA GLUCOSE) .. 7 B. ANION GAP (AG).. 8 C. CREATININE CLEARANCE (CCR) .. 9 10 10 RECOMMENDED 11 Traceability and Uncertainty of Measurement for Medical Laboratories2009-04-14 Page 2 of 11 2009 Quality Management Program laboratory Services. All Ontario laboratory Accreditation program documents are the sole property and copyright of the Quality Management Program laboratory Services, ALL RIGHTS RESERVED. No part of the material protected by this copyright may be reproduced without written permission from QMP LS. The logos and/or symbols used are the property of QMP LS or other third parties. You are not permitted to use these logos and/or symbols without written permission from QMP LS or such third party that may own the logos and/or symbols.

4 SCOPE The purpose of this document is to provide the following information for accredited medical laboratories: an understanding of the concept of Measurement Traceability , within which determination of Uncertainty of Measurement is required; an explanation of the applicable accreditation requirements; suitable ways to obtain Uncertainty of Measurement results for examinations included within the scope of medical laboratory accreditation. INTRODUCTION Ontario laboratory Accreditation (OLA) first outlined its expectations with regard to Traceability and Uncertainty of Measurement in the medical laboratory in QMP LS News; No. 118, September 2007, ( Traceability and Uncertainty of Measurement for Medical Laboratories OLA s Expectations ).

5 1 The article pointed out that Traceability and Uncertainty of Measurement ensure valid laboratory measurements, in concert with method validation, quality control and quality assurance. By establishing both the Traceability and Uncertainty of Measurement of quantitative measurements, the laboratory establishes and demonstrates the preciseness of its methods, determines if repeat results are measurably different, and demonstrates that its results are fit-for-purpose (measuring the desired component). Ensuring that laboratory measurements are valid requires the use of appropriate reference materials for method validation, calibration, Traceability , estimation of Uncertainty and quality control/quality assurance.

6 For medical testing, Traceability and Uncertainty of Measurement are essential and usually overlapping components. In order to receive an accreditation certificate from QMP LS, OLA s accreditation requirements must be met. The applicable requirements (version , July 2008) 2 that specifically address calibration/ Traceability and Uncertainty of Measurement are: for calibration/ Traceability ; and for Uncertainty of Measurement . Traceability and Uncertainty of Measurement for Medical Laboratories2009-04-14 Page 3 of 11 2009 Quality Management Program laboratory Services. All Ontario laboratory Accreditation program documents are the sole property and copyright of the Quality Management Program laboratory Services, ALL RIGHTS RESERVED.

7 No part of the material protected by this copyright may be reproduced without written permission from QMP LS. The logos and/or symbols used are the property of QMP LS or other third parties. You are not permitted to use these logos and/or symbols without written permission from QMP LS or such third party that may own the logos and/or symbols. Traceability DEFINITION Traceability (Tr) Property of the result of a Measurement or 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. (Source: Standards Council of Canada CAN-P-1626 Policy on Traceability requirements for calibration sources used by accredited testing laboratories).

8 3 CONCEPT Traceability provides confidence in the trueness of a Measurement result, and it is characterized by six sub-components: 1. an unbroken chain of comparisons going back to an acceptable national or international set of references; 2. Uncertainty of Measurement (calculated or estimated for each step in the chain by agreed methods and stated as such to allow overall Uncertainty to be calculated or estimated for the entire process); 3. documentation; 4. competence (evidence of technical competence); 5. reference to SI Units (where possible, chain of comparisons must end with reference to primary standards that are traceable to SI units); 6.

9 Calibration intervals (length, number of variables, Uncertainty required, frequency of use, etc.). Merely stating that results are obtained against a manufacturer s reference material or that the method is standardized against a standard/reference available from a reference body is not sufficient to ensure Traceability of results. OLA REQUIREMENTS OLA requirement states All calibration material and devices shall be traceable to an accepted reference standard that is expressed in SI units whenever applicable. The laboratory shall have a mechanism to ensure accuracy if the information is not available from the The guidance information provided with this requirement explains that it is expected that a program for calibration of measuring systems and verification of trueness will be designed and performed to ensure that results are traceable to SI units or by reference to a natural constant or other stated reference.

10 Recognizing that Traceability to a reference preparation is not always possible or relevant in medical testing, examples of other means for providing confidence in the results are suggested: participation in inter- laboratory comparisons; use of suitable reference materials, certified to indicate the characterization of the material; examination or calibration by another procedure; ratio or reciprocity-type measurements; mutual consent standards or methods that are clearly established, specified, characterized and mutually agreed upon; and Traceability and Uncertainty of Measurement for Medical Laboratories2009-04-14 Page 4 of 11 2009 Quality Management Program laboratory Services.