個體化醫(yī)療的現(xiàn)狀與未來-生物標志物

個體化醫(yī)療的現(xiàn)狀與未來

四.生物標志物研究M.D.,Ph.D.Outline生物標志物的概念如何評價生物標志物？生物標志物的研究方法？生物標志物的概念什么是生物標志物(biomarker)？“measurableandquantifiablebiologicalparameters”--aMedicalSubjectHeading(MeSH)term,1989“Acharacteristicthatisobjectivelymeasuredandevaluatedasanindicatorofnormalbiologicalprocesses,pathogenicprocessesorpharmacologicalresponsestoatherapeuticintervention.”--BiomarkerDefinitionsWorkingGroup,2001,NIH

FeaturesofaUsefulBiomarkerHighsensitivityandspecificityEasyaccessiblesampleCorrelationwithhistologicalscoringChangeinadvanceofclinicalsignsTranslationalfromresearchtoclinicaluse不同水平生物標志物DNAPrimarytranscriptmRNATranscriptionproteinTranslationRNAprocessingNucleusBiomarkerExamplesCholesterolisoneofthemostwell-knownbiomarkersofcardiovascularhealthPhysicalmeasurements:bodytemperature(fever);bloodpressure(strokerisk)Otherbiomarkers:?bloodsugarlevel(diabetes)?antigens(hepatitis)?proteins(heartattack)?geneticvariations(Huntington’sdisease)生物標志物的臨床應(yīng)用LudwigJAetal.Naturereviews2005,5:845-856目前臨床很多疾病的診斷依賴病理診斷，但不能作為常規(guī)篩查、監(jiān)測手段眾多疾病缺乏早期、特異性生物標志物治療缺乏個體化方案生物標志物應(yīng)用現(xiàn)狀ClinJAmSocNephrol3:1895–1901,2008.BiomarkersforchronickidneydiseaseArewetreatingsub-populations?疾病藥物無反應(yīng)率抑郁SSRIs,SNRIs,TCAs40-60%哮喘?-adrenergics,LTD44-75%糖尿病Sulfonylurea,Biguanides,Glitazones50-75%腫瘤(乳腺癌肺癌)Various70-100%FromKalow,Tyndale&Meyer,Pharmacogenomics,2001NovelbiomarkersareneededEarly,accuratediagnosis-IndividualizedtherapyandimprovedtreatmentoutcomesBetterdefinedpopulationswillallowmorespecificdrugs-Betterefficacy-Fewersideeffects“Theuseofbiomarkerswillchangemedicalpracticefromapopulation-basedapproachtoan

individualizedapproach”

FelixFrueh,AssociateDirectorofGenomicsatCDER,FDAEvolutionofthebiomarkersresearchHighplasmacholesterolandcardiovasculardiseasesNearly50percentofallfuturemyocardialinfarctionandstrokeeventsoccurinthosewithnormalorbelownormallipidlevels.EUROASPIREStudyGroup,1997%ofMIAdditionalbiomarkers(inflammation)

Hs-CRPandcardiovascularriskHs-CRPisthemostwidelystudiedbiomarkerofinflammationincardiovascularrisk.Sincetheearly1990swiththedevelopmentofhighlysensitiveassaysforitsmeasurement,correlationsofhs-CRPwithbothcardiovascularriskfactorsandfuturecardiovasculareventshasbeenpossible.CRPandLDL–ClevelsandtheriskofcardiovasculardiseasesC-ReactiveProtein(mg/L)<1.01.0-3.0>3.0<130130-160>160LDL-cholesterol(mg/dL)3.02.01.00.0MultivariableRelativeRiskIncreasedCRPlevelsareassociatedwithincreasedriskofcardiovasculareventsindependentlyofLDL-ClevelsRidkerPMetal.,200227,939womenHighCRP-highLDLHighCRP-lowLDLLowCRP-lowLDLLowCRP-highLDLPorbabilityofEvent-freeSurvivalYearsofFollow-up0.990.980.970.960.001.0002468Evolutionofthebiomarkersresearch:

CRPandLDL-Clevelsandevent-freesurvivalamongwomen27,939womenThemedianvalueswereasfollows:C-reactiveprotein:1.52mg/LLDLcholesterol:123.7mg/dLor:3.20mmol/LCRPandLDL-Ccouldgivebetterprognosticinformationthanthetwomarkersseparately.RidkerPMetal.,2002如何評價生物標志物？

常用評價指標（一）敏感性（二）特異性（三）Youden指數(shù)（四）陽性似然比（五）陰性似然比（六）陽性預(yù)報值（七）陰性預(yù)報值（八）ROC曲線ECG診斷試驗的結(jié)果ECG診斷結(jié)果心肌梗塞合計出現(xiàn)不出現(xiàn)陽性陰性合計416(TP)9（FP）425104(FN)171（TN）275520180700(N)一、敏感性（Sensitivity):TP/(TP+FN)=TPR(truepositiverate)TRP=Sen=416/(416+104)=0.8該指標只與病例組有關(guān)，反映了診斷試驗檢出病例的能力ECG診斷試驗的結(jié)果ECG診斷結(jié)果心肌梗塞合計出現(xiàn)不出現(xiàn)陽性陰性合計416(TP)9（FP）425104(FN)171（TN）275520180700(N)二、特異性（Specificity)Spe=Truenegativerate(TNR)=TN(FP+TN)=171/(171+9)=0.95該指標只與對照組有關(guān)，反映了診斷試驗排除非病例的能力。靈敏度與特異度的優(yōu)缺點優(yōu)點：靈敏度與特異度不受患病率的影響，其取值范圍均在（0,1）之間，其值越接近于1，說明其診斷準確性越好。缺點：當比較兩個診斷試驗時，單獨使用靈敏度或特異度，可能出現(xiàn)矛盾。解決辦法：將兩指標結(jié)合：Youden指數(shù)、陽性似然比、陰性似然比等ECG診斷試驗的結(jié)果ECG診斷結(jié)果心肌梗塞合計出現(xiàn)不出現(xiàn)陽性陰性合計416(TP)9（FP）425104(FN)171（TN）275520180700(N)三、Youden指數(shù)，=Sen+Spe-1=TPR-FPR=0.8-0.05=0.75Youden指數(shù)取值范圍在（0，1）之間，其值越接近1，診斷準確性越好。ECG診斷試驗的結(jié)果ECG診斷結(jié)果心肌梗塞合計出現(xiàn)不出現(xiàn)陽性陰性合計416(TP)9（FP）425104(FN)171（TN）275520180700(N)ECG診斷試驗的結(jié)果ECG診斷結(jié)果心肌梗塞合計出現(xiàn)不出現(xiàn)陽性陰性合計416(TP)9（FP）425104(FN)171（TN）275520180700(N)醫(yī)生最關(guān)心的問題：

1.試驗陽性時患病的概率多大？

2.試驗陰性時不患病的概率多大？陽性預(yù)測值是在診斷試驗陽性的受試者中，標準診斷有病的病例（真陽性）所占的比例陰性預(yù)測值則是在診斷試驗為陰性的受試者中，標準診斷證實無病的受試者（真陰性）所占的比例。ECG診斷結(jié)果心肌梗塞合計出現(xiàn)不出現(xiàn)陽性陰性合計416(TP)9（FP）425104(FN)171（TN）275520180700(N)陽性預(yù)報值與陰性預(yù)報值ROC曲線

ROC（receiveroperatingcharacteristic的縮寫，譯為“接受者工作特征”）ROC曲線研究歷史1950’s雷達信號觀測能力評價1960’s中期實驗心理學(xué)、心理物理學(xué)1970’s末與1980’s初診斷醫(yī)學(xué)ROC的涵義與起源不同診斷界值時

靈敏度與特異度間的平衡(tradeoff)0204060801005060708090100特異度靈敏度百分率（％）ReceiverOperatingCharacteristiccurve

AreaUnderCurve(AUC)-GraphedCurve1=.50Purechance…nobetterthanrandomguessCurve3isbetterthanCurve2Curve4=1.0TotallySensitivecompletelyaccurateclassificationofeffectivelyandless-effectivelyinstructedstudents完美與無用的ROC曲線真陽性率即靈敏度假陽性率即1－特異度機率線(chanceline)

(diagonalreferenceline)診斷準確度較低（<0.7）0.00.20.40.60.81.00.00.20.40.60.81.0FPRTPRA＝0.664A＝0.830診斷準確度較高（>0.9）0.00.20.40.60.81.00.00.20.40.60.81.0FPRTPRA＝0.938ROC曲線下面積（Area）與診斷準確度高低高0.90-1.00=excellent(A)中0.80-0.90=good(B)0.70-0.80=fair(C)低0.60-0.70=poor(D)0.50-0.60=fail(F)ROC曲線小結(jié)ROC曲線反映了靈敏度與特異度間的平衡

(增加靈敏度將降低特異度；增加特異度將降低靈敏度)。

在ROC曲線空間，如果曲線沿著左邊線，然后沿著上邊線越緊密，則試驗準確度越高。

在ROC曲線空間，如果曲線沿著機會線（45度對角線）越緊密，則試驗準確度越低。

ROC曲線下面積是重要的試驗準確度指標。

生物標志物研究方法phasePhase1PreclinicalExploratoryPhase2ClinicalAssayandValidationPhase3RetrospectiveLongitudinalPhase4ProspectiveScreeningPhase5DiseasecontrolObjectiveTargetbiomarkeridentification,feasibilityStudyassayinpeoplewithandwithoutdiseaseCase-controlstudiesusingspecimensLongitudinalstudiestopredictdiseaseClinicaluseSiteBiomarkerdevelopmentlabBiomarkervalidationlabClinicalepidemiologiccentersCohortstudiesCommunityDesignCross-sectionalCross-sectionalCase-controlprospectiveRCTSamplesizesmallsmallmodestmediumlargeVasanRS.Circulation.2006;113:2335-2362.TheAgendiaMammaPrintTest首個FDA批準的基因組檢測試驗--Feb.2007Howtheygotthere？2002–Discoveryof70genesignature(117patients)2002–Duplicationofresults(inanothersampleset:295patients)2006–Assayperformance2006–Optimizedarrayformat:reproducibility;backtooriginalsampleset2006–Externalconfirmation(307patients,5hospitals)2007–ApprovalbyFDA生物標志物研究技術(shù)傳統(tǒng)研究方法：PCR,Westernblotting,ELISA,etal新型研究方法：基因組學(xué)技術(shù)蛋白質(zhì)組學(xué)技術(shù)：2-DIGE/MS,蛋白質(zhì)芯片生物標志物研究方法Question1.Whathumansamplesshouldbecollected,andhowshouldtheybeused?Doesthisvarybetweendiscovery,validationandimplementation?Answer1.AllbiologicalsamplesareeligibleforcollectionCollectedbiologicalmaterialdependsonanalyteandtissuesourceExamples–Biologicalfluids?Serum,plasma,urine,csf?Secretions?Saliva,seminalfluid

–

Bodycavityfluids

?Pleuralfluid,peritonealfluid,etc–Specifictissuematerial?Specializedcells–reproductivecells–Non-cellularIdeal–Biomarkerdiscoverysamplesshouldbeidenticaltotheprojectedtestingsituation–(e.g.Donotstudyplasmafordiscovery,andthenvalidateorimplementassayusingserum)Practical–setupstudywithsamplesthatareasclosetothetestingsituationaspossibleQuestion2.Whatistheroleofroutinelyaccessiblebiofluidssuchasplasma,serum,andurine?Whatistheroleof“proximal”fluidslikeCSF,synovialfluid,ascites,pancreaticductalfluid,etc?Whatistheroleofsolidtissues?RoleofroutinelyaccessiblebiofluidsVeryimportantinthediscoveryofbiomarkersofdiseases(systemicvs.organspecific/local)Importantfor:–earlydetection–diseaseseverity–tumorburden–prognosis–monitoringofres