Uncertain of the UKAS Requirements?

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
Accreditation Standards

• Certification Bodies
• EN 45011
• EN 45012
• EN 45013

• Laboratories
• ISO 17025
• Inspection Bodies
• EN 45004

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
Management Requirements

• 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

10
Technical Requirements

• 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

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
Validation of Methods

• Accuracy
• LOD
• Selectivity
• Linearity
• Repeatability
• Reproducibility
• Robustness
• Interferences

• Validate over the range
• Validate for the scope
• Is this something new??.

13
Validation of Methods

• Validation data needs to be used..
• Meeting the clients 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