Quality Control: Lj Chart And Westgard Multirule.

WESTGARDRULESWestgardhasformulatedrulestodecidewhetherananalyticalrunisin-controoroutofcontrol.Theserulescanbeappliedassinglerulesandasagroupofrules(multi-rules).WestgardrulescanbeappliedonlyifourQCsareplottedwiththerangeof3SD.RuleCRITERIASUSPECTEDEXAMPLE12sOnemeasurementexceeds2standarddeviationseitheraboveorbelowthemeanofthereferencerange.Itisawarningrule.Failureofthisruledoesnotalwaysindicateananalyticalerrorhasoccurred.Ifthecontrolfallsoutsideofthe2slimitbecauseofanormalGaussiandistribution,thenextcontrolresultshouldpassthisrule.InaccuracyandorImprecision13sOnemeasurementexceeds3standarddeviationseitheraboveorbelowthemeanofthereferencerangeThismaybetheresultofrandomerrorandshouldbeinvestigated.InaccuracyandorImprecision22s2consecutivemeasurementsexceed2standarddeviationsofthereferencerange,andonthesamesideofthemean.Thisrulecanapplytoasinglelevelduring2consecutiverunsorbothlevelsofcontrolduringthesamerun.Violationsuggestssystematicerror.InaccuracyR4sTwomeasurementsinthesamerunhavea4standarddeviationdifference(suchasoneexceeding2standarddeviationsabovethemean,andanotherexceeding2standarddeviationsbelowthemean).Thisrulealsoappliesbetweencontrollevels.Onecontrolisbeyondthe+2slimitandtheotherisbeyondthe-2slimit.Violationsuggestsrandomerror.Imprecision41s4consecutivemeasurementsexceed1standarddeviationonthesamesideofthemean.Thisrulecaninvolveoneorbothcontrollevels.Violationsuggestssystematicerror.inaccuracy10x10consecutivemeasurementsareonthesamesideofthemean.Thisrulecanapplywithinonecontrollevelorbetweencontrollevels.Failureofthisruleindicatesashiftandthepresenceofsystematicerror.InaccuracyLEVEY-JENNINGSCHARTALevey-Jenningschartisagraphthatqualitycontroldataisplottedontogiveavisualindicationwhetheralaboratorytestisworkingwell.Thedistancefromthemeanismeasuredinstandarddeviations.EXAMPLE:CONTROL1:Mean-200mg/dl,SD:4mg/dlUppercontrollimit(2s):200+2*4=208,lowercontrollimit(2s):200-2*4=192Uppercontrollimit(3s):200+3*4=212,lowercontrollimit(3s):200-3*4=188CONTROL2:Mean-250mg/dl,SD:5mg/dlUppercontrollimit(2s):250+2*5=260,lowercontrollimit(2s):250-2*5=240Uppercontrollimit(3s):250+3*5=265,lowercontrollimit(3s):250-3*5=235Levey-JenningsQC:Cholesterolexamplewhere:Control1hasameanof200mg/dLandstandarddeviationof4.0mg/dL.Control2hasameanof250mg/dLandstandarddeviationof5.0mg/dL.Prepareappropriatecontrolchartsandinterprettheresults.DayControl1ValueControl2Value12sRuleViolation13sRuleViolationAccept(A),Warning(W),orReject(R)?Comments1200247A2205250A3195255A4202243A5186254-2s-3sR6207263+2sW(A)7194251A8209264+2stwiceRBothexceed+2s.9200253A10196244A11190261+2sand-2sRbothexceed2sinoppositedirections.12204254A13196239-2sW(A)14207236-2sR2daysinarowexceeding-2s.15200250A16205259A17209257+2sW(A)18197256A19196249A20198257A21197241A22195255A23198250A24199259A25191247-2sW(A)Negativeshift.26197242A27190256-2sW(A)Followtoseeifnegativeshiftcontinuesorworsens.28202246AInterpretationofcontrolresults-with12sand13srules:Useofa12sruleasastrictrejectionrulewouldresultinrejectingrunsondays5,6,8,11,13,14,17,25,and27,foratotalof9runs,asshownbythecheckmarksinthecolumnfor12sruleviolations.Useofa13srejectionrulewouldleadtorejectionofonlyonerunonday5,asshownbythesinglecheckmarkinthecolumnfor13sruleviolations.12sreferstothecontrolrulethatiscommonlyusedwithaLevey-Jenningschartwhenthecontrollimitsaresetasthemeanplus/minus2s.Inmanylaboratories,thisruleisusedtorejectarunwhenasinglecontrolmeasurementexceedsa2scontrollimit.13scorrespondstoaLevey-Jenningscharthavingcontrollimitssetasthemeanplus/minus3s.Ananalyticalrunisrejectedwhenasinglecontrolmeasurementexceedsa3scontrollimit.The12sruleisverycommonlyusedtoday,andwhileitprovideshigherrordetection,theuseof2scontrollimitsgivesanexpectedhighleveloffalserejections.The13sruleprovidesanalternativeQCprocedurethathaslowerfalserejections,butalsolowererrordetection.