Proficiency testing catalogue - LGC Standards

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Frequently askedquestionsbut those results that are out of the range ofthe assigned value ± 5 x SDPA will beexcluded and the robust mean and standarddeviation will then be recalculated. Theserecalculated values will be used for thestatistical analysis. By removing these‘blunders’ from the dataset any influenceon the summary statistics is completelyremoved. All results, including excludedresults, will be given z-scores.Q: What could be the cause of my poorperformance?A: A single poor result is not indicative of overalllaboratory performance but neither is asingle good result. Ideally, PT results shouldbe monitored over time to detect unusual biasor repeated unsatisfactory results indicatepoor performance.There are many possible reasons for a singleunsatisfactory result including statisticalchance. It is therefore important to interpretthe results from PT schemes within thecontext of an all-round quality assuranceprogramme, including internal quality control,use of validated methods and referencematerials.There are numerous potential causes ofunsatisfactory performance in a PT schemewhich may include analytical andnon-analytical errors:Analytical errors• Calibration / instrument problems;• Extraction / clean-up;• Interferences / matrix effects;• Diagnostic kits / reagents;• Analyst / method performance.Non-analytical errors• Calculation / transcription;• Reporting format / units;• Storage;• Test material defects.Test materials are subjected to rigorous qualitycontrol testing before being distributed toparticipants, and are unlikely to be the causeof a poor z-score.All possible reasons for a poor performanceshould be investigated fully in order to identifythe most likely cause and to enable actionto be taken to prevent recurrence. Repeattest materials are available after everydistribution, but it is most important toinvestigate and understand the reason(s)for the failure, document this fully, and carryout corrective actions before repeating a test.Q: How can I measure my laboratory’sperformance over time?A: You can do this by Trend Analysis. A singleresult simply reflects the performance of thelaboratory on the particular day that the testwas carried out and therefore gives limitedinformation. Frequent participation in PTschemes over time can give greater insightinto long-term performance and can helpidentify where internal bias may be occurring.One of the best methods of summarisingz-scores over time is graphically as this givesa clear overview and is less prone tomisinterpretation than numerical methods.Participants are therefore advised to monitortheir PT results over time. Further informationregarding interpretation and trend analysisof proficiency results is given in the IUPAC“International Harmonised Protocol for theProficiency Testing of Analytical ChemistryLaboratories”, 2006 and ISO 13528.Trend Analysis is an integral part of ourPORTAL software.Q: How can I graphically plot and analysetrends for qualitative results?A: Qualitative results are difficult to depictgraphically as they are not normally allocateda performance score. However for qualitativeresults, a correct result could be allocated a60 Tel: +44 (0)161 762 2500 Fax: +44 (0)161 762 2501
performance score of 0 to represent asatisfactory result. A false positive result canbe represented by a performance score of+ 3, whilst a false negative result can berepresented by a performance score of - 3.If plotted graphically over time, this shouldgive a clear visual indicator of performancein qualitative tests.Q: How will I receive my report?A: Following statistical evaluation of the results,the reports will be available on the websitewithin 4 to 15 working days of round closure(see specific scheme description). Participantswill be emailed a link to the report when it isavailable. The contents of reports vary fromscheme to scheme but include details of thecomposition of test materials, the assignedvalues, and tabular and/or graphicalrepresentations of participants’ results.Paper copies are also available for anadditional charge.Q: My results have not been included in thereport can I calculate my performancez score?A: To calculate your performance score pleasevisit www.lgcpt.com/portal Select ‘help’from the menu and download the z scorecalculatorQ: How can I receive advice and feedback?A: Communication with participants will becarried out through scheme-relateddocumentation, e-mails, letters, newsletters,memos, fax, or through LGC Standardslocal offices. Open meetings may also beorganised and all interested parties invitedto attend.Q: How can I send feedback?A: Comments on any aspect of our productsand services are welcome either by phone,fax, letter, email or by contacting your localLGC Standards office.Q: How do I assess the reproducibilitystandard deviation from the PT report?A: The robust standard deviation provided inthe PT report for a specific method can betaken as an estimate of the reproducibilitystandard deviation for the PT round for thatspecific method.Q: Can I have a report that only includes mygroup laboratories?A: Yes we can produce reports tailored to acustomer’s specific requirement. There willbe an additional charge for administrationand computer programming costs.Copyright to all reports remains with LGCStandards Proficiency Testing but permission isgranted to participants to make copies for theirown internal use, for example for quality controland regulatory purposes. No other copies maybe made without obtaining permission.Email: customerservices@lgcpt.comWebsite: www.lgcpt.com61
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Proficiencytestingcatalogue
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Introduction• LGC Standards• Ai
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IntroductionAim of proficiency test
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IntroductionTypical scheme cycle fr
Page 9 and 10: • AFPSAnimal feeds scheme• QCSC
Page 11 and 12: Analyte group Number of distributio
Page 13 and 14: QCS - Chocolate schemeThe Quality i
Page 15 and 16: QFCS - Food chemistry schemeThe Qua
Page 17 and 18: QMAS - Meat schemeThe Quality in Me
Page 19 and 20: • AquacheckWater chemistry scheme
Page 23 and 24: Test materialAnalytesTest materialA
Page 25 and 26: Test materialAnalytesTest materialA
Page 27 and 28: Test materialMetals:Soil, Acid Extr
Page 29 and 30: QWAS - Water microbiology schemeThe
Page 31 and 32: • QBSBeverage scheme• BAPSBrewi
Page 35 and 36: BAPS - Brewing analytes schemeThe B
Page 37 and 38: MAPS - Malt analytes schemeThe MAPS
Page 39 and 40: • PACQSParticle analysis andchara
Page 43 and 44: PHARMASSURE - Pharmaceutical scheme
Page 45 and 46: QMIS - Microbiology investigation s
Page 47 and 48: TOYTEST - Toy safety schemePlay is
Page 49 and 50: • Special bespoke microbiologytes
Page 51 and 52: Closed customised PT schemesReferen
Page 53 and 54: Frequently askedquestions
Page 55 and 56: isk associated to the measurements.
Page 57 and 58: transcribe results correctly. LGC S
Page 59: Q: How do I interpret my results?A:
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Page 65 and 66: PolandAgnieszka WojdaLGC Standards
Page 67: Global quality management nt soluti
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Proficiency testing catalogue - LGC Standards

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