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Uncertain of the UKAS Requirements?

Uncertain of the UKAS Requirements?. Lorraine Turner. Uncertain of the UKAS Requirements?. Accreditation in the UK Standards used - ISO 17025 Requirements for validation of methods Requirements for estimating uncertainty Approaches to estimating uncertainty

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Uncertain of the UKAS Requirements?

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  1. Uncertain of the UKAS Requirements? Lorraine Turner

  2. Uncertain of the UKAS Requirements? • Accreditation in the UK • Standards used - ISO 17025 • Requirements for validation of methods • Requirements for estimating uncertainty • Approaches to estimating uncertainty • What UKAS assessors are looking for • Qualitative Testing

  3. Laboratory Accreditation in the UK • 1966 British Calibration Service (BCS) • 1981 National Testing Laboratory Accreditation Service (NATLAS) • 1985 National Measurement Accreditation Service (NAMAS) • 1995 United Kingdom Accreditation Service (UKAS)

  4. UKAS • Formed in 1995 • Company limited by guarantee • Memorandum of Understanding with government through DTI • Recognised by the UK government as the sole national body for accreditation • Represents UK in ILAC, EA and IAF

  5. Accreditation “ Formal recognition that an organisation is competent to carry out specific tasks or types of task” • Impartial, independent assessment of competence against international standards

  6. Certification Bodies EN 45011 EN 45012 EN 45013 Laboratories ISO 17025 Inspection Bodies EN 45004 Accreditation Standards

  7. ISO 17025 • General requirements for the competence of testing and calibration laboratories • International Standard published in 2000 • Replaces ISO Guide 25, EN45001 and NAMAS Standard M10

  8. ISO 17025 • Standard has 2 parts • Requirements for sound management • Requirements for technical competence

  9. Organisation Quality System Document Control Contract Review Subcontracting Purchasing supplies Service to client Complaints Non-conforming work Corrective Action Preventive Actions Audits and Reviews Records Management Requirements

  10. Personnel Accommodation and Environment Methods and Validation Uncertainty of measurement Equipment Measurement Traceability Sampling Handling of Test Items Quality Assurance Internal QC Proficiency Testing. Reporting include MU where relevant Technical Requirements

  11. Validation Requirements “Validation is the confirmation by examination and the provision of objective evidence that the particular requirements for a specific intended use are fulfilled” (ISO 17025 5.4.5.1) Validation is always a balance between costs/risks and technical possibilities

  12. Accuracy LOD Selectivity Linearity Repeatability Reproducibility Robustness Interferences Validate over the range Validate for the scope Is this something new??…. Validation of Methods

  13. Validation of Methods Validation data needs to be used……….. • Meeting the client’s requirements • Estimating Measurement Uncertainty

  14. Uncertainty “ A parameter, associated with the result of the measurement, that characterises the dispersion of the values that could reasonably be attributed to the measurand” ISO Definition

  15. Measurement Uncertainty in ISO 17025 • Calibration labs and test labs carrying out in-house calibrations (5.4.6.1) • “shall have and apply a procedure” • Testing Labs (5.4.6.2) • “shall have and apply procedures” • “nature of the test may preclude rigorous…” • “..based on knowledge of performance… …previous experience and validation data”

  16. Measurement Uncertainty • Degree of rigor needed depends on factors such as…. • requirements of the method • requirements of the client • limits for conformance to a specification ISO 17025 5.4.6.2 Note 1

  17. Information to help • ISO Guide to the expression of uncertainty in measurement • ILAC/EA documents • Eurachem/CITAC Guide • UKAS Publications M3003 and Lab 12 • BMTA/NMP Good Practice Guide (no. 36)

  18. Summary of the Steps • Identify what is being measured • List factors that may affect measurements • eliminate insignificant • Quantify the components • Type A: Statistical analysis of repeated observations • Type B: other • Combine • Calculate the expanded uncertainty (k factor)

  19. But you have validated methods!!!! • Examine your validation (and QC) data • Compare with factors list • Are there any other factors? • Quantify other factors/Carry out further validation

  20. What are we looking for? • Estimate of precision • obtained from (ideally) reproducibility and incorporates a high degree of variability • Estimate of bias and its uncertainty • from a CRM/spiking experiments • Other factors? • Further validation studies may be required to fill in any gaps • Estimate of uncertainty (+/-)

  21. Qualitative Testing • Detection tests • Confirmation tests • Identification tests • Characterisation tests • Comparison tests Does the concept of uncertainty apply??

  22. Qualitative Testing • Identify and control sources of uncertainty • Establish limit of detection and its uncertainty • Establish specificity • Demonstrate consistency of interpretation between analysts

  23. “Maturity of the mind is the capacity to endure uncertainty” John Finley (1908-1974) English Historian and Mathematician

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