Guidelines for Laboratory Testing and Result Reporting of Antibody to Hepatitis C VirusWord文档下载推荐.docx
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WendiL.Kuhnert,Ph.D.
LynFinelli,Dr.P.H.
DivisionofViralHepatitis
NationalCenterforInfectiousDiseases
ThematerialinthisreportoriginatedintheNationalCenterforInfectiousDiseases,JamesM.Hughes,M.D.,Director,andtheDivisionofViralHepatitis,HaroldS.Margolis,M.D.,Director.
Summary
TestingforthepresenceofantibodytohepatitisCvirus(anti-HCV)isrecommendedforinitiallyidentifyingpersonswithhepatitisCvirus(HCV)infection(CDC.RecommendationsforpreventionandcontrolofhepatitisCvirus[HCV]infectionandHCV-relatedchronicdisease.MMWR1998;
47[No.RR-19]:
1--33).Testingforanti-HCVshouldincludeuseofanantibodyscreeningassay,andforscreeningtest-positiveresults,amorespecificsupplementalassay.Verifyingthepresenceofanti-HCVminimizesunnecessarymedicalvisitsandpsychologicalharmforpersonswhotestfalselypositivebyscreeningassaysandensuresthatcounseling,medicalreferral,andevaluationaretargetedforpatientsserologicallyconfirmedashavingbeeninfectedwithHCV.However,substantialvariationinreflexsupplementaltestingpracticesexistsamonglaboratories,andananti-HCV--positivelaboratoryreportdoesnotuniformlyrepresentaconfirmedpositiveresult.Theseguidelinesexpandrecommendationsforanti-HCVtestingtoincludeanoptionforreflexsupplementaltestingbasedonscreening-test--positivesignal-to-cut--off(s/co)ratios.Useofs/coratiosminimizestheamountofsupplementaltestingthatneedstobeperformedwhileimprovingthereliabilityofreportedtestresults.TheseguidelinesweredevelopedonthebasisofavailableknowledgeofCDCstaffinconsultationwithrepresentativesfromtheFoodandDrugAdministrationandpublichealth,hospital,andindependentlaboratories.Adoptionoftheseguidelinesbyallpublicandprivatelaboratoriesthatperforminvitrodiagnosticanti-HCVtestingwillimprovetheaccuracyandutilityofreportedanti-HCVtestresultsforcounselingandmedicalevaluationofpatientsbyhealth-careprofessionalsandforsurveillancebypublichealthdepartments.
Introduction
TeststodetectantibodytohepatitisCvirus(anti-HCV)werefirstlicensedbytheFoodandDrugAdministration(FDA)in1990
(1).Sincethattime,newversionsoftheseandotherFDA-approvedanti-HCVtestshavebeenusedwidelyforclinicaldiagnosisandscreeningofasymptomaticpersons.
Personsbeingtestedforanti-HCVareentitledtoaccurateandcorrectlyinterpretedtestresults.CDChasrecommendedthatapersonbeconsideredtohaveserologicevidenceofHCVinfectiononlyafterananti-HCVscreening-test--positiveresulthasbeenverifiedbyamorespecificserologictest(e.g.,therecombinantimmunoblotassay[RIBA®
;
ChironCorporation,Emeryville,California])oranucleicacidtest(NAT)
(2).ThisrecommendationisconsistentwithtestingpracticesforhepatitisBsurfaceantigenandantibodytohumanimmunodeficiencyvirus(HIV),forwhichlaboratoriesroutinelyconductmorespecificreflextestingbeforereportingaresultaspositive(1,3).However,foranti-HCV,themajorityoflaboratoriesreportapositiveresultbasedonapositivescreeningtestresultonly,anddonotverifytheseresultswithmorespecificserologicornucleicacidtestingunlessorderedbytherequestingphysician.Unfortunately,certainhealth-careprofessionalslackanunderstandingoftheinterpretationofanti-HCVscreeningtestresults,whenmorespecifictestingshouldbeperformed,andwhichtestsshouldbeconsideredforthispurpose.
Incertainclinicalsettings,false-positiveanti-HCVresultsarerarebecausethemajorityofpersonsbeingtestedhaveevidenceofliverdiseaseandthesensitivityandspecificityofthescreeningassaysarehigh.However,amongpopulationswithalow(<
10%)prevalenceofHCVinfection,false-positiveresultsdooccur(4--11).Thisisofconcernwhentestingisperformedonasymptomaticpersonsforwhomnoclinicalinformationisavailable,whenpersonsarebeingtestedforHCVinfectionforthefirsttime,andwhentestingisbeingusedtodeterminetheneedforpostexposurefollow-up.Withoutknowledgeoftheoriginofthetestsampleorclinicalinformationconcerningthepersonbeingtested,theaccuracyofascreening-test--positiveresultforanygivenspecimencannotbedetermined.
Multiplereasonsexistregardingwhylaboratoriesdonotperformreflexsupplementaltestingforanti-HCV,includinglackofanestablishedlaboratorystandardforsuchtesting,lackofunderstandingregardingtheperformanceandinterpretationofthescreeningandsupplementalHCVtests,andthehighcostofthesupplementalHCVtests.Tofacilitatepracticeofreflexsupplementaltesting,therecommendedanti-HCVtestingalgorithmhasbeenexpandedtoincludeanoptionthatusesthesignal-to-cut--off(s/co)ratiosofscreening-test--positiveresultstominimizethenumberofspecimensthatrequiresupplementaltestingandprovidearesultthathasahighprobabilityofreflectingtheperson'
strueantibodystatus.
Background
AvailableAnti-HCVScreeningAssays
FDA-licensedorapprovedanti-HCVscreeningtestkitsbeingusedintheUnitedStatescomprisethreeimmunoassays;
twoenzymeimmunoassays(EIA)(AbbottHCVEIA2.0,AbbottLaboratories,AbbottPark,Illinois,andORTHO®
HCVVersion3.0ELISA,Ortho-ClinicalDiagnostics,Raritan,NewJersey)andoneenhancedchemiluminescenceimmunoassay(CIA)(VITROS®
Anti-HCVassay,Ortho-ClinicalDiagnostics,Raritan,NewJersey).AlloftheseimmunoassaysuseHCV-encodedrecombinantantigens.
AvailableSupplementalTests
Supplementaltestsincludeaserologicanti-HCVassayandNATsforHCVRNA.IntheUnitedStates,theonlyFDA-licensedsupplementalanti-HCVtestisthestripimmunoblotassay(ChironRIBA®
HCV3.0SIA,ChironCorp.,Emeryville,California).RIBA3.0usesbothHCV-encodedrecombinantantigensandsyntheticpeptides.Becauseitisaserologicassay,itcanbeperformedonthesameserumorplasmasamplecollectedforthescreeninganti-HCVassay.
FDA-approveddiagnosticNATsforqualitativedetectionofHCVRNAusingreversetranscriptasepolymerasechainreaction(RT-PCR)amplificationincludeAMPLICOR®
HepatitisCVirus(HCV)Test,version2.0andCOBASAMPLICOR®
HepatitisCVirusTest,version2.0(RocheMolecularSystems,Branchburg,NewJersey),whichhavealowerlimitofdetectionofapproximately50IU/mL(12).DetectionofHCVRNAbythesetestsrequiresthattheserumorplasmasamplebecollectedandhandledinamannersuitableforNATandthattestingbeperformedinalaboratorywithfacilitiesestablishedforthispurpose(seeRecommendations).OtherNATsforHCVRNA,bothqualitativeandquantitative,areavailableonaresearch-usebasisfrommultiplemanufacturersofdiagnosticreagents,andcertainlaboratoriesperformNATsbyusingin-houselaboratorymethodsandreagents(12,13).
InterpretingAnti-HCVTestResults
ScreeningImmunoassayTestResults
Anti-HCVtestingincludesinitialscreeningwithanimmunoassay.Criteriaforinterpretationofareactive†anti-HCVimmunoassayresultarebasedondatafromclinicalstudiesperformedundertheauspicesofeachmanufacturer.ForEIAs(e.g.,HCVEIA2.0andHCVVersion3.0ELISA),specimenswithareactiveresultareretestedinduplicate.Iftheresultofeitherduplicatetestisreactive,thespecimenisdefinedasrepeatedlyreactiveandisinterpretedasscreening-test--positive.ForCIAs,(e.g.,VITROSAnti-HCVassay),specimenswithasinglereactiveresultareconsideredscreening-test--positiveanddonotrequireretesting.
ThespecificityoftheHCVEIA2.0andHCVVersion3.0ELISAis>
99%.However,amongapopulationwithalowprevalenceofinfection,evenaspecificityof99%doesnotprovidethedesiredpredictivevalueforapositivetest.Amongimmunocompetentpopulationswithanti-HCVprevalences<
10%(e.g.,volunteerblooddonors,activedutyandretiredmilitarypersonnel,personsinthegeneralpopulation,health-careworkers,orclientsattendingsexuallytransmitteddisease[STD]clinics),theproportionoffalse-positiveresultswithHCVEIA2.0orHCVVersion3.0ELISAaveragesapproximately35%(range:
15%--60%)(4--11;
CDC,unpublisheddata,2002).Amongimmunocompromisedpopulations(e.g.,hemodialysispatients),theproportionoffalse-positiveresultsaveragesapproximately15%(14;
CDC,unpublisheddata,2002).Forthisreason,notrelyingexclusivelyonanti-HCVscreening-test--positiveresultstodeterminewhetherapersonhasbeeninfectedwithHCViscritical.Rather,screening-test--positiveresultsshouldbeverifiedwithanindependentsupplementaltestwithhighspecificity.
SupplementalSerologicTestResults
Thestripimmunoblotassay(RIBA),asupplementalanti-HCVtestwithhighspecificity,isperformedonscreening-test--positivesamplesandprovidesresultsthatareinterpretedaspositive,negative,orindeterminate.ApositiveRIBAresultisinterpretedasanti-HCV--positive(Box).Althoughthepresenceofanti-HCVdoesnotdistinguishbetweencurrentorpastinfection,aconfirmedanti-HCV--positiveresultindicatestheneedforcounselingandmedicalevaluationforHCVinfection,includingadditionaltestingforthepresenceofvirus(NATforHCVRNA)andliverdisease(e.g.,alanineaminotransferase[ALT])(2,15).Anti-HCVtestingusuallydoesnotneedtoberepeatedaftertheanti-HCV--positiveresulthasbeenconfirmed.
AnegativeRIBAresultisinterpretedasanti-HCV--negativeandindicatesafalse-positivescreeningtestresult.Inthissituat
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