Driving laboratory quality through proficiency testing · 2014-12-02 · The primary aim of...
Transcript of Driving laboratory quality through proficiency testing · 2014-12-02 · The primary aim of...
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Driving laboratory quality through proficiency testing
Science for a safer world
Measurements
Measurement
Health
Security
Trade
Compliance Decisions
Reliable measurements
Reliable decisions
Overview
PT within the quality assurance system
Purpose, types and benefits of PT
Selecting appropriate PT schemes
Interpretation of PT results
Method Validation
Calibration Training
IQC
Quality Assurance System
? Measurement
System Input Output
RMs
PT
Fit-for-purpose analysis requires:
Careful development and validation of methods
Accurate calibration of instruments and appropriate equipment
Qualified and competent staff
Comparability with measurements made in other laboratories
Well defined QC and QA procedures
Independent evidence of performance
CRMs
Traceable Standards
RMs & PT
RMs
RMs & QC
PT
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Proficiency Testing – purpose and types
What is PT?
The primary aim of proficiency testing is:
“To provide the infrastructure for a laboratory to monitor and improve the quality of its routine analytical measurements”
• PT provides an objective evidence of the competence of the participant which can be used to
– Improve the performance of the participant
– Give confidence in the participant’s ability to perform a specific measurement
• PT provides information on other aspects of the management system
– Reception/treatment of the sample, treatment of the data, result reporting etc
Types of PT
• Various types of PT available – based on one or more elements of four different categories:
Qualitative
Quantitative
Interpretive
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Descriptive – nominal or ordinal scale
Numeric – interval or ratio scale
No measurement involved
Types of PT
• Various types of PT available – based on one or more elements of four different categories:
Qualitative
Quantitative
Interpretive
Pre-measurement
Measurement
Post-measurement
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2
Types of PT
• Various types of PT available – based on one or more elements of four different categories:
Qualitative
Quantitative
Interpretive
Sequential
Simultaneous
Pre-measurement
Measurement
Post-measurement
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3
2
Monitor Performance Report
Sequential participation scheme structure
PT Provider
Test Item
Test Result
Test Result
Test Result
Monitor Performance
Monitor Performance
Lab 1
Lab 2
Lab 3
PT P r o v i d e r
Evaluation of
Results
Lab 1
Lab 2
Lab 3
NMi
Simultaneous scheme structure
PT Provider
Test Items
Participating Laboratories
Test Results
PT Provider
Evaluation of
Results Report
Participating Laboratories
Monitoring Performance
Types of PT
• Various types of PT available – based on one or more elements of four different categories:
Qualitative
Quantitative
Interpretive
Single
Continuous
Sequential
Simultaneous
Pre-measurement
Measurement
Post-measurement
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3
2
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Use of PT by laboratories
• Basic use of PT for a laboratory is:
– to assess its performance for the conduct of specific measurements or calibrations
• Results and information received from participation will provide laboratories with:
– Confirmation that the laboratory’s performance is satisfactory
– An indication that there are potential problems and that corrections should be made
• However, the use of PT should be much wider
– Many additional benefits from PT participation
Benefits of PT to laboratories
Benefits of PT
Performance Comparison
Independent Check
Performance comparison
Benefits of PT to laboratories
Benefits of PT
Method/ Procedure Evaluation
Performance Comparison
Independent Check
Method/instrument comparison
Benefits of PT to laboratories
Benefits of PT
Method/ Procedure Evaluation
Performance Comparison
Monitoring Trends
Independent Check
Monitoring trends
Benefits of PT to laboratories
Benefits of PT
Third Party Demonstration
Method/ Procedure Evaluation
Performance Comparison
Monitoring Trends
Independent Check
Training and Education
Maximising the benefits of PT
• To obtain the optimum benefit from PT participation, laboratories should: – treat PT scheme test items as routine samples (i.e. do not
give them any special treatment) – vary the analyst testing the test items – vary the instrumentation used for the test items
• To learn from PT participation, laboratories should: – use the scheme results to give feedback to laboratory
procedures and staff; both positive and negative – use the scheme results constructively – be honest; the scheme is there to help – Education not regulation
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Selecting the right PT
Selecting the right PT scheme
• Selection of a PT scheme is critical if the benefit is to be maximised
• All laboratories need to develop an adequate PT participation strategy – Aim to participate in relevant PT schemes, at an appropriate frequency
for the laboratory’s circumstances
• Five key questions 1) What level of PT and frequency do I need? 2) Do any PT schemes exist for the technical competence required? 3) Is the PT scheme relevant? 4) Is the PT provider competent i.e. do they operate to ISO/IEC 17043? 5) Is the selected PT scheme independent of any manufacturing or
marketing interests in equipment, reagents or calibrators?
Strategy of PT participation
• Important to consider a number of different aspects
• Other QA measures implemented: - Use of CRMS - Comparisons by independent techniques - Participation in validation or characterisation studies - Use of internal QC measures - Other laboratory comparisons
• Level of risk: - No measurements undertaken - Turnover of technical staff - Staff experience/knowledge - Known stability/instability of measurement technique - Significance and final use of data
• Different types of PTs can be used
• Difficulty of PT participation e.g. technical characteristics of the measurement, low number of laboratories etc
• Legislative requirements for frequency of type of participation
Fit for purpose PT schemes
• Need to decide which scheme is fit for purpose – Often a scheme will not have a perfect fit, so need to find the
best fitness for purpose
• A number of factors to consider
– Test Items
– Distribution
– Participants
– Results
– Reports
– PT Provider
Test items
‘Real’ sample Simulated sample
Real sample:
• Familiar format
• Similar challenges to routine samples
Simulated sample:
• Homogenous
• Stable
Test items
• Parameters: – Routinely tested parameters – Standard reporting units – Available at an appropriate frequency
• Concentrations: – Appropriate for the range in which the
laboratory is working – Significantly different levels will not
reflect on routine testing at the laboratory’s normal levels
Distribution
• Distribution dates available
• Distributions monthly, bi-monthly, quarterly, 6-monthly or annual
• Flexible participation available
• Fit-for-purpose
Participants
• National/international – Languages – regional offices – Transport
• Participating laboratories – Private/public – Test methods used
Results
• Deadlines
• Methods of returning results
• Confidentiality
• Statistical approach – Available to participants – Easy to understand – Consistent – Summary statistics – Graphs – Trend analysis
Reports
• Speed of reporting
• Language of documentation
• Information in reports – scores – graphs – tables – technical feedback – method information
• Format of report e.g. electronic version or paper copy
PT Provider
• Experience
• Scope
• Competence – Complies with ISO/IEC
17043
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Interpretation of PT results
Performance evaluation
• Limited value unless performance is evaluated
• Evaluate after each round and also over time
• Interpretation of PT performance concerns all management levels
• PT is not about “passing” or “failing” – it is about learning from the results
Review of single PT round performance
• Results of each PT round should be evaluated regardless of performance
– A satisfactory result may not mean good performance – Unsatisfactory performance in one round does not indicate
that the laboratory is not competent
• Important to consider a number of factors: – The overall results in the round
– Test method performance
– Test item factors
– Bi-modal result distribution
– PT Scheme factors
Trends in PT performance
• Trends are valuable in preventive and corrective actions, and root cause analysis
– Performance over time
– Common groups of determinands
– Performance of methods
– Performance of analysts
Need for an investigation
• All laboratories will occasionally have unsatisfactory or questionable PT results
• A laboratory should establish its own criteria for when an investigation is necessary
• The depth of investigation will depend on a number of factors:
– Criticality of the method
– Frequency of unsatisfactory results
– Evidence of a bias
Causes of unsatisfactory performance
• Can be analytical and non-analytical
• Both are equally serious – the result reported is the important factor for a laboratory
• Analytical Errors – Calibration – Instrument problems – Extraction/clean-up – Interferences – Method performance – Analyst
• Non-Analytical Errors – Calculation – Transcription – Units – Reporting format
PT – in conclusion
PT is an essential tool to all laboratories making measurements
PT participation brings many benefits
PT enables measurements to be monitored and improved
PT is a very powerful quality assurance tool
underpinning laboratory accreditation
PT drives laboratory quality
PT Reliable Measurements
Reliable Decisions