Description:

ChromogenixCoatest®APC™ResistanceisanAPTT-basedassaykitforthedetectionoftheAPCresistancephenotype,i.e.thepooranticoagulantresponsetoactivatedproteinC(APC).Thetestresult(APCratio)givesanestimationoftheanticoagulantfunctioninvivoandprovidesinformationonthethromboticriskassociatedwithinheritedandacquiredAPCresistance.DetectstheAPCresistancephenotyperegardlessofitscause.DetectsbothinheritedandacquiredAPCresistance.

MeasurementPrinciple:

PlasmaisincubatedwiththeAPTTreagentforastandardperiodoftime.CoagulationisinitiatedbytheadditionofCaCl2intheabsenceandpresenceofAPCandthetimeforclotformationisrecorded.

ActivatedProteinC(APC)isaregulatorofthecoagulationcascade,byspecificallyinactivatingfactorsVaandVIIIa,inthepresenceofphospholipidsandcalcium. Inmostofthecases(morethan90%),ActivatedProteinCResistance(APCR)phenotypeiscausedbyaFactorVgenemutation.

ActivatedProteinCResistanceistestedbyusingaclottingmethodperformedwithorwithoutActivatedProteinC. ChromogenixCoatest®APC™Resistance,whichdoesnotinvolvepre-dilutionwithFV-deficientplasma,detectstheAPCresistancephenotyperegardlessofitscause(inheritedandacquiredAPCresistance).

Background:

ActivatedproteinC(APC)isakeyanticoagulantenzymeneededfortheproperdown-regulationofbloodcoagulation.ApooranticoagulantresponsetoAPC,denotedAPCresistance,isarecentlydescribedblooddefectfoundtobeamajorriskfactorforvenousthromboembolisminWesternsocieties.Atleast90%ofcaseswiththeAPCresistancephenotypecanbeexplainedbyapointmutationinthecoagulationfactorVgene,changingarginine506inthefactorVmoleculetoglutamine.Afteractivation,mutatedfactorV(denotedFV:Q⁵⁰⁶orFactorVLeiden)ispartiallyresistanttoinactivationbyAPC,whichallowsforlongerdurationofthrombingenerationandmayleadtoahypercoagulablestate.APCresistanceduetothepresenceoftheFV:Q⁵⁰⁶alleleisinheritedasanautosomaldominanttraitandhasaprevalenceof2-13%inthegeneralpopulation.FrequenciesofAPCresistanceamongpatientswithvenousthrombosis,dependingontheselectioncriteria,rangefrom20-60%.ThehighprevalenceofAPCresistance,combinedwiththeavailABIlityofsimplebloodtestsbywhichitisdetected,raisesthequestionofwhethergeneralscreeningforAPCresistanceshouldbeperformedinconjunctionwithcircumstantialriskfactorsforthrombosissuchassurgery,pregnancyandoralcontraceptives.Readmore…