Understanding NELAC Proficiency Testing Requirements

1
Understanding NELAC Proficiency Testing
Requirements

• Chuck Wibby
• Laboratory Specialty Conference Expo
• Irving, Texas
• May 31, 2002

2
Presentation Overview

• The Role and Benefits of PTs
• History of PT Program
• NELAC PT Program
• Which PTs Do You Need?
• Successful PT Compliance
• DMRQA?
• Recent Developments

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Where PTs Fit In
Quality System
On-Site Assessment
Proficiency Testing
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Benefits of PTs

• Selecting a Commercial Lab
• Lab Quality Assurance
• Performance Based Measurement Systems
• Common Deficiencies
• Lab Fraud
• PTs are a recurring objective evaluation of a
  labs performance

5

• Brief History
• of
• PT Program

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History

• Late 70s EPA started DMRQA, WS and WP programs
• 1995- Decision to Privatize Program
• 1995-1998 EPA, NIST NVLAP and NELAC worked
  together to develop privatized program
• 1998 Last EPA programs
• 1999 First Privatized Programs

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• NELAC
• PT Program

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NELAC PT Program

• http//www.epa.gov/ttn/nelac/
• Chapter 2 and Associated Appendices
• May 24, 2001 Version
• NELAC PT FOT Tables
• April 2002 Version
• EPA National Standards for Water Proficiency
  Testing Studies
• NIST NVLAP Handbook 150-19

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NELAC PT Program

• Chapter 2
• 2.2 Major groups PT Providers, PTOB/PTPA, Labs,
  AAs
• 2.3 Requirements for PT Providers
• 2.4 2.5 Requirements for Labs
• 2.6 Evaluation of Results
• 2.7 Criteria for Accreditation

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NELAC PT Program

• Chapter 2 Appendices
• A PT Provider Approval Criteria
• B PT Sample Design and Acceptance
• C PT Acceptance Criteria
• D PTOB/PTPA
• E Micro
• F WET
• G Radiochemistry
• H Field Air

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NELAC PT FOTs
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• Which PTs
• Do You Need?

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NELAC Accreditation

• NELAC Accreditation
• Matrix
• Technology/Method
• Analyte/Analyte Group

• NELAC PT (1999)
• Regulatory Program
• Matrix
• Analyte
• NELAC PT (2001)
• Matrix
• Technology/Method
• Analyte/Analyte Group

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Start with YourScope of Accreditation

• Waste Water
• Method 200.7
• Analytes
• Al
• Sb
• Etc..

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Cross Reference to PT FOT Tables

• If analyte is on your Scope of Accreditation and
  in the applicable NELAC FOT Table, you need to
  analyze a PT that includes the analyte.
• Can use the same PT standard for multiple methods
• Ex ICP-OES and GFAA

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• Successful
• PT Compliance

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2 of most recent 3

• Only thing that matters is Acceptable
• Check for Error Acceptable
• Maintain record of two of most recent three and
  youre accredited

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Example
19

• Establishing
• Acceptance Limits

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NELAC Acceptance Limits

• Fixed Limits
• 15
• Centered on assigned value (100 concentration)
• Regression equations
• Centered on expected mean recovery
• Regression equation SDs
• Combinations
• Centered on study mean
• Regression equation SDs

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Regression equations
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Regression equations

• Y mx b
• a, b, c, d????
• Predicted mean (Lab Result a) b
• Predicted SD (Lab Result c) d
• WS Acceptance Limits Pred mean 2 Pred SD
• WP Acceptance Limits Pred mean 3 Pred SD

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• Why PTs
• Are
• Different

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PTs and real samples

• PTs actually contain analytes (lots of them)
• Come in ampules and require dilution
• DQOs are different (from method and customer
  requirements)
• Very important (actual and perceived value)

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PTs Have Changed

• EPA changed program when it was privatized
• Analytes can be left out
• More analytes
• 220 in old program
• 450 in new program
• Soon to be method specific

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• DMRQA

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DMRQA

• DMRQA
• Not NELAC compliant
• Time frame is longer than 45 days
• Subset of WP analytes

• WP
• Is NELAC compliant
• Can be used for DMRQA
• NELAC WET PTs DMRQA WET PTs

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• Recent
• Developments

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Recent Developments

• Proficiency Testing Reporting Limits (PTRLs)

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PTRLs
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PTRL Footnote

• NELAC Proficiency Testing Reporting Limits
  (PTRLs) are provided as guidance to laboratories
  analyzing NELAC PT samples. At a minimum, the
  laboratory should use a method that is sensitive
  enough to generate quantitative results at the
  PTRLs shown...

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PTRL Footnote

• ... NELAC PTRLs are also provided as guidance to
  PT Providers. At a minimum for all analytes with
  an assigned value equal to "0", the PT Provider
  should verify that the PT sample does not contain
  the analyte at a concentration greater than or
  equal to the PTRL.

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How PTRLs Were Derived

• Calculate lowest possible acceptance limit
• Estimate at 50 of lowest possible concentration
• Some reality review

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How to use PTRLs

• For analytes with an assigned value gt0
• Selection of method
• Reality check on result
• For analytes with the possibility of an assigned
  value 0 (VOAs, Semis, Pests)
• Guide to reporting low level positive results

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Thank You!

• Chuck Wibby
• 303-940-0033
• cwibby_at_wibby.com