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![Variance Index Score (VIS)
Proposed by United Kingdom’s National
External Quality Assessment Service (UKNEQAS)
VIS = (%Variation/CCV) X 100
• CCV = Chosen CV
• % Variation =
[ (lab result-Designated value) / Designated Value ] X
100
• Designated Value Mean after recalculating
outlier values (>3SD)
Interpretation of PT result](https://image.slidesharecdn.com/proficiencytestingforgclpbydrpd-250816053128-4fa75e52/75/Proficiency-Testing-for-GCLP-by-Dr-PD-pptx-16-2048.jpg)
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Proficiency Testing for GCLP by Dr PD.pptx
- 1. Testing The Testers:Proficiency Testing for Lab Excellence Dr. PRIYANKADATTA ASSISTANT PROFESSOR DEPT. OF BIOCHEMISTRY BANKURASAMMILANI MEDICAL COLLEGE MD, PGDHHM
- 2. Also Called EQA Proficiencytesting (PT) is a process for assessing laboratory performance by which multiple laboratories analyze common samples and an outside entity collects and evaluates the results. • Internal QC is necessary for daily monitoring of the precision and accuracy of the analytical method, and external QA is important for the maintenance of long term accuracy of analytical methods. • Monitor Lab results by an external agency Retrospectively to assess the Accuracy and estimate Bias
- 3. History • Belk andSunderman first PT program in late 1940s • In India first in 1977 at CMC Vellore • Biorad, RIQAS (Randox) • - CAP Surveys (USA) • - NEQAS (UK) • ISHTM- AIIMS & IAMM for Hematology and Microbiology • MAX ,NEU QAP,Metropolis
- 4. Participants Organising laboratory/Company Prepare EQA SamplesExamine samples Analyse results Report results Prepare report Evaluate Principle of EQA Schemes
- 5. • All participatinglaboratories analyzing the same PT material, sent by the PT provider • PT results are tabulated monthly and are sent to the provider for data analysis. • Summary reports are prepared by the program sponsor and are distributed to all participating laboratories.
- 6. • What isthe purpose of EQA Challenge participants quality systems Encourage inter-laboratory comparability Encourages improvement Provides insight into national /international levels of performance Allows poor performance to be addressed Excellent source of reference material Required in licensing (accreditation)
- 7. • What isa good EQA scheme Internationally recognised Has many participating laboratories Numerous and varied samples Several distributions throughout the year Rapid report turnaround Preferably electronic result entry and report return Educational
- 8. Selecting a PTProvider • Choose ISO/IEC 17043 accredited providers • Ensure provider offers your test analytes • Check NABL recognition list regularly • Confirm reporting, logistics and cost suitability • Documentation support and scoring formats
- 9. How to Runa PT Sample? Treat it Exactly as any other Patient sample How NOT to Run a PT Sample? 1. Extra/Unscheduled Calibration/ Maintenance on the day of PT sample run 2. Repeat the sample more than usual, give the mean 3. Fix a specific Technician for the task
- 11. The overall meanof all laboratories in the program or the mean of values of all the participating laboratories, is taken as the “true or correct value” and is used or comparison with the individual laboratory’s result
- 12. 1. SDI 2. ZScore 3. VIS 4. En Number Interpretation of PT result
- 13. Interpretation of PTresult SDI- Standard Deviation Index SDI = (Lab result – Group Mean)/Group SD SDI≥ 2 Warning Signal SDI ≥ 3 Unacceptable and Needs urgent RCA and CAPA
- 14. Z score Two types. • Classical Z score Essentially, Same as SDI • Robust Z Score Better in non-gaussian distribution of results • Robust Z Score = (Normalized Lab Result – Group median)/ Normalized IQR *NIQR = IQR X 0.7413 RMZ= Running Mean Z-score. An ongoing (within or across cycles) average of the Z-scores of the last six samples for a given analyte. Interpretation of PT result
- 16. Variance Index Score(VIS) Proposed by United Kingdom’s National External Quality Assessment Service (UKNEQAS) VIS = (%Variation/CCV) X 100 • CCV = Chosen CV • % Variation = [ (lab result-Designated value) / Designated Value ] X 100 • Designated Value Mean after recalculating outlier values (>3SD) Interpretation of PT result
- 17. CCV of somecommon analytes (CCV essentially designates TEa for that Analyte)
- 19. En Number :expanded uncertainty of the assigned value and the participants result is taken Interpretation of PT result x = result reported by participant X = assigned value
- 20. PT/EQA in ISO15189 and NABL Accreditaion • Mandatory to participate in any commercially available and accredited PT program, for every parameter under scope • If no PT program available in India- • Only few laboratories performing the test. • Analyte to be measured is unstable e.g., blood gases, ammonia, G6PD. • Then Alternative approaches may be used
- 21. In ISO 15189: 2022 – Clause 7.3.7.3 a) The laboratory shall monitor its performance of examination methods, by comparison with results of other laboratories. This includes participation in EQA programs appropriate to the examinations and interpretation of examination results, including POCT examination methods. b) The laboratory shall establish a procedure for EQA enrollment, participation and performance for examination methods used, where such programs are available. c) EQA samples shall be processed by personnel who routinely perform pre- examination, examination, and post-examination procedures. d) The EQA programme(s) selected by the laboratory shall, to the extent possible: have the effect of checking pre-examination, examination, and post-examination processes; 2) provide samples that mimic patient samples for clinically relevant challenges; 3) fulfill ISO/IEC 17043 requirements.
- 22. In ISO 15189: 2012 – Clause 5.6.3
- 23. In ISO 15189: 2022 – Clause 7.3.7.3 g) EQA data shall be reviewed at regular intervals with specified acceptability criteria, in a time frame which allows for a meaningful indication of current performance.
- 24. Example of PTResult- Biorad EQAS
- 27. •Peer level ofcomparison is used when other laboratories use the same analyte, method, instrument, and reagent combination as yours. •If <9 results are received for Your Peer, your comparison is Your Method for a uni-modal distribution or Your Mode for a multi-modal distribution of data.
- 29. The Yundt Plotshows your samples Z‑scores, arranged by concentration of the reported samples along the bottom of the chart. A line of best fit is shown allowing for a determination of test bias by concentration of the samples analyzed. Yundt Plot
- 30. The statistics shownare a result of grouping the results based on instrument, method, and reagent combination
- 33.
- 39. Interpreting Unsatisfactory Performance • Isolatedfailures may be random errors • Repeated failures suggest systemic issues • Analyze analyte-specific and operator trends • Check IQC during same period • Trigger RCA and corrective action if needed
- 43. CAPA After PTFailure • Immediate correction of identified error • Preventive actions to avoid recurrence • Retrain staff and revise SOPs if needed • Verify effectiveness through follow-up QC • Record CAPA in quality documentation
- 44. Common Errors inPT Participation • Wrong units or decimal placement • Sample mix-up or labeling errors • Late result submission to provider • Data entry errors in online portal • Improper storage or preparation of sample
- 45. Challenges in PTImplementation • Limited PT schemes for rare parameters • Cost burden for small or rural labs • Delays in sample delivery/logistics • Digital reporting barriers • Lack of PT awareness in some settings
- 46. Overcoming PT Challenges •Use inter-lab comparisons for rare tests • Simulate PT using blind samples internally • Form regional PT networks and groups • Seek NABL or academic collaborations • Promote digital support tools
- 47. Summary and KeyTakeaways • PT ensures accuracy and patient safety • It is mandatory for ISO 15189 and NABL • Failure triggers RCA and CAPA • Use PT data for continual improvement • Treat PT as a tool, not a burden
Editor's Notes
- #4 If the laboratory performs poorly on EQA, the problems may lie anywhere along the path of workflow. All aspects of the process will need to be checked. Problems may lie anywhere in the testing process: pre-testing, testing, and post-testing. Most problems occur in the pre and post analytic phase of testing. The integrity of the specimen may have been compromised during preparation, shipping or after receipt by improper storage or handling. Problems such as with reagents, test methods, quality control, or competency of staff may occur during testing. Due to the numbers of specimens collected and transported by various test sites, care must be taken to ensure proper transcription of data throughout the testing process
- #6 EQA helps to assure customers, such as Physicians, patients, and health authorities, that the laboratory can produce reliable results. Individual laboratories can use EQA to identify problems in laboratory practices, allowing for appropriate corrective action. EQA participation will help to evaluate reliability of methods, materials, and equipment, and to evaluate and monitor training impact. For laboratories performing public health-related testing, EQA can help to assure that results from different laboratories during surveillance activities are Comparable. EQA is important for improvement of the laboratory quality management system, as it is a measure of laboratory performance. Samples received for EQA testing, as well as the information shared by the EQA provider, are useful for conducting continuing education activities.
- #7 Internationally recognised Has many participating laboratories Numerous and varied samples Several distributions throughout the year Rapid report turnaround Preferably electronic result entry and report return Friendly and helpful – advice in trouble-shooting Educational
- #8 Always select a PT provider accredited to ISO/IEC 17043. NABL publishes a list of approved providers. Confirm that the provider offers schemes for your analytes, uses appropriate sample matrices, and provides clear result formats. Make sure reporting timelines and support services are practical and reliable. Scoring criteria, platform compatibility, and affordability are also key considerations.
- #39 Not every PT failure is a cause for alarm—sometimes it’s a random error. However, repeated failures point to underlying problems. Investigate trends across analytes, instruments, and operators. Review IQC results for the same period. If errors are consistent, this should trigger a Root Cause Analysis and appropriate corrective and preventive actions.
- #43 Once you identify the root cause, you must take action. Corrective actions fix the current problem—like recalibration or replacing reagents. Preventive actions are meant to avoid recurrence—such as revising SOPs or retraining staff. Always verify that your actions worked using follow-up QC or audits. All CAPA activities must be documented and reviewed in quality meetings.
- #44 Even simple mistakes can lead to PT failure. Common issues include reporting in wrong units, misplacing a decimal, or mixing up samples. Delays in submission or incorrect data entry also affect performance grading. In some cases, samples may degrade due to incorrect storage or preparation. Establish internal checks to catch these before submission.
- #45 PT implementation is not always smooth. Some tests don’t have available PT schemes. Logistics in rural areas may cause sample delays or spoilage. Cost can be prohibitive for smaller labs. Also, not all labs are comfortable with online submission platforms or reports in English. These barriers must be acknowledged and addressed.
- #46 Solutions exist for PT barriers. You can conduct informal inter-lab comparisons for parameters without formal PT. Internally simulate PT using blind-coded samples. Labs in similar regions can collaborate to create shared PT pools. Encourage professional bodies or universities to support regional PT. Also push for user-friendly platforms and multilingual reports.
- #47 To conclude: PT ensures your lab results are accurate and reliable, which is critical for patient safety. It’s a non-negotiable requirement under ISO 15189 and NABL. Any failure must be analyzed, corrected, and prevented. PT also helps improve internal processes and staff competence. Instead of seeing it as a burden, embrace PT as a quality tool.