传染病流行病学7.how to read medical literature(201.11.70(1).pptx

Howtoreadmedicalliterature 1 Prof LuCiyongDepartmentofEpidemiologyandMedicalStatistics Contents 2 Gainaccurateandreliableinformationtoguideclinicalpractice scientificresearchandteachingKnowmoreabouttheareawhichyouareinterestedinKeepupwiththelatestprogressofthesubjectProvideasolutionforaissueyouarecurrentlyfacingObtainideaandinspirationofstudydesign Objectives 3 AccordingtothecontentandstructurePrimarystudiesSecondarystudies AccordingtothemediaPrintElectronic Classificationofliterature 4 1 GuyattGH SackettDL SinclairJC HaywardR CookDJ CookRJ User sguidetothemedicalliterature IX Amethodforgradinghealthcarerecommendations JAMA 1995 274 1800 4 Primarystudies 1 Sometimesknownasempiricalstudiesreportresearchfirst handRandomizedcontrolledtrialsOthercontrolledclinicaltrialsCohortstudiesCase controlstudiesCross sectionalsurveysCasereports Classificationofliterature 5 ForexamplesRandomizedcontrolledtrials 6 METHODS Adolescents ages12 18years withsevereobesity BMI 1 2timesthe95thpercentileorBMI 35kg m2 wererecruitedforthisdouble blind randomized placebo controlledtrial Participantscompleted4weeksofmealreplacementtherapyfollowedbyrandomization 1 1 toeither24weeksoftopiramate75mg dayorplacebo Meanchangeswerecomparedbetweengroups Classificationofliterature Secondary orintegrative studies 2 AttempttosummarizeanddrawconclusionsfromprimarystudiesOverviewsnon systematicreviews whichsummarizeprimarystudiessystematicreviews whichdothisusingarigorous transparentandauditablemethodmeta analyses whichintegratethenumericaldatafrommorethanonestudy Classificationofliterature 7 2 TrishaGreenhalgh HowtoReadaPaper Thebasisofevidence basedmedicine FourthEdition 2010 Wiley Blackwell BMJBooks 8 GuidelinesdrawconclusionsfromprimarystudiesabouthowcliniciansshouldbebehavingDecisionanalysesusetheresultsofprimarystudiestogenerateprobabilitytreestobeusedbybothhealthprofessionalsandpatientsinmakingchoicesaboutclinicalmanagement Classificationofliterature ForexamplesMeta analyses 9 Classificationofliterature MethodsWesoughtdatafromlargeprospectivestudies 100000participantsatbaseline orlargemulti cohortconsortia total 100000participantsatbaseline WeidentifiedstudiespublishedfromJanuary 1970 toJanuary 2015 throughsystematicliteraturesearchesanddiscussionwithinvestigators ElectronicsearchesweredonewithMEDLINE Embase andScopus andwiththeterms body massindex mortality or death cohort or prospective andcombinationsofthewords risk relative ratio hazard or rate 10 Figure1 Asimplehierarchyofevidence Classificationofliterature ExamplesofelectronicdatabasesPubMedWebofScience MedlineEMBASECochraneLibraryCINAHL CumulatedIndexofNursingandAlliedHealthLiterature BiosisPreviewsGlobalHealthScopusGoogleorGoogleScholar Medicalinformationdatabase 11 Classificationofliterature 12 Classificationofliterature CommonlyunifiedconstructionTitleAbstractandKeywordsIntroduction orBackground MethodsResultsDiscussionandConclusionsReferencesAdditionalinformation ifany endnotes acknowledgement institutionalaffiliationoftheauthorsandgrantsupport Constructionofmedicalliterature 13 TitleThecoreofthewholepaper subject studyfactor andoutcome WheresearchengineslookforkeywordsandfortopicsAnexampleApaperentitled Mechanicalventilationguidedbyesophagealpressureinacutelunginjury subjects humanoranimal studydesign RCToranythingelse outcome survivalratesorthetimeofstay Thismaybebetter Survivalratesofmechanicalventilationguidedbyesophagealpressureinpatientswithacuterespiratorydistresssyndrome ARDS arandomizedcontrolledstudy 14 Constructionofmedicalliterature AbstractProvidethemostimportantfactsfoundinthestudy150 300words usuallyincluding Background orHypothesis MethodsResultsConclusions 15 Constructionofmedicalliterature 16 Constructionofmedicalliterature Anexample KeywordsRevealthetopicoftheliterature3 8wordsorphrasesAllthekeywordsprovidedshouldbeselectedfromthemostcurrentissueofmedicalsubjectheadingsofIndexMedicusIndexMedicus MedicalSubjectHeadings MeSH 17 Constructionofmedicalliterature Introduction orbackground Whytheauthorsdecidedtodothisparticularpieceofresearch Statethebackgroundtotheresearch followedbyabriefreviewofthepublishedliteratureStateclearlytheresearchquestionsand orthehypothesisAnswerthequestion Studywhat why 18 Constructionofmedicalliterature MethodsHowtheydidit ThissectionshouldprovidetheenoughdetailsoftheexperimentandtheproceduresthatsomeoneelsecouldexactlyrepeatthestudyReadercanjudgethepotentialforsuccessoftheexperimentandassessifcorrectstatisticalmethodswereusedAnswerthequestion Howdidthestudyperform 19 Constructionofmedicalliterature MethodsincludingExperimentcondition thesourceoftheanimal species gender age weight healthcondition entercriterion feeding Experimentmethod instrument reagent manufacturers Subjects source hospitalorcommunity sampling randomizedornot enterandexclusioncriterion thewaytodividegroups Studydesign cross sectionalstudy casecontrolstudy cohortstudy RCT Intervention themedicine theplacebo dose frequencies exposurepathways ThewaytocontrolthequalityofthestudyThestatisticalmethods 20 Constructionofmedicalliterature ResultsWhattheyfound EachelementofdatadescribedintheMethodssectionshouldbereportedintheResultssection eitherinthetextorinfiguresortablesNointerpretationsofthedatashouldbereportedintheResultssection butstatisticalanalysis levelofsignificanceandprobabilitiesofdifferenceshouldbereportedhereAnswerthequestion Whatdidthestudyfind 21 Constructionofmedicalliterature BasicstatisticsinResults 22 Constructionofmedicalliterature BasicstatisticsintheResults DiscussionMeaningofresultsDifferencesfromprevioussimilarstudiesandexplainwhySupportingevidencefromotherstudiesLimitationsandshortcomingsSpeculationofimportanceFutureworkrecommendationsAttention Nonewdatashouldberevealedinthissection 23 Constructionofmedicalliterature ConclusionsSomejournalsrequireaseparateConclusionssectionOnlythoseactuallytestedinthestudyandconfirmedtobevalidbystatisticalanalysisOftenidenticaltothoseintheabstract 24 Constructionofmedicalliterature PaperConstruction 25 SuggestedOrderofReadingaPaper 26 Constructionofmedicalliterature StudydesignObservationalstudycross sectionalstudycasecontrolstudycohortstudy Experimentalstudyrandomizedcontrolledtrial RTC Theoreticalstudy 27 TheWaytoReadDifferentTypesofStudy Cross sectionalsurveysArepresentativesampleofparticipantsisrecruitedandtheninterviewed examinedorotherwisestudiedtogainanswerstoaspecificclinicalquestionIncross sectionalsurveys dataarecollectedatasingletimepointbutmayreferretrospectivelytohealthexperiencesinthepastforexample thestudyofpatients medicalrecordstoseehowoftentheirbloodpressurehasbeenrecordedinthepast5years 28 TheWaytoReadDifferentTypesofStudy Biasincross sectionalsurveysSelectionbiasnon response refusalbias isdueto ConvenienceSampleViolatedrandomsamplingscheme ReportingbiasExposuremaybeunder reportedbecauseofattitudes perceptions orbeliefs 29 TheWaytoReadDifferentTypesofStudy Case controlstudiesPatients withaparticulardiseaseorconditionareidentified Controls patientswithsomeotherdisease thegeneralpopulation neighborsorrelatives Dataarethencollected e g bysearchingbackthroughthesepeople smedicalrecords orbyaskingthemtorecalltheirownhistory onpastexposuretoapossiblecausalagentforthedisease 30 TheWaytoReadDifferentTypesofStudy Matched Biasincase controlstudiesRecallbiasResultsfromdifferentialabilityofsubjectstorememberpreviousactivitiesandexposuresBerkson sbiasAhospital basedcase controlstudy MightfindalinkbetweentwodiseasesorbetweenanexposureandadiseasewhenthereisnoassociationbetweentheminthegeneralpopulationPrevalence incidencebiasTheexposureofthecasesmightbechangedafterdevelopingthedisease 31 TheWaytoReadDifferentTypesofStudy CohortstudiesTwo ormore groupsofpeopleareselectedonthebasisofdifferencesintheirexposuretoaparticularagent suchasavaccine amedicineoranenvironmentaltoxin Followeduptoseehowmanyineachgroupdevelopaparticulardiseaseorotheroutcome 32 TheWaytoReadDifferentTypesofStudy Attention Thefollow upperiodincohortstudiesisgenerallymeasuredinyears andsometimesindecades sincethatishowlongmanydiseases especiallycancer taketodevelop BiasincohortstudiesDifferentiallosstofollow upBiasduetodifferencesincompletenessoffollow upbetweencomparisongroupsDetectionbiasTheexposurepromotedmorecarefulevaluationfortheoutcomeofinterestInterviewerbiasSystematicdifferenceinsoliciting recording interpretinginformation 33 TheWaytoReadDifferentTypesofStudy Randomizedcontrolledtrials RCTs Participantsinthetrialarerandomlyallocatedtoeitheroneintervention suchasadrugtreatment oranother suchasplacebotreatment Bothgroupsarefollowedupforaspecifiedtimeperiodandanalyzedintermsofspecificoutcomesdefinedattheoutsetofthestudy e g death heartattack andsoon Attention Onaverage thegroupsareidenticalapartfromtheintervention anydifferencesinoutcomeare intheory attributabletotheintervention RCTisthegoldstandardinmedicalresearch 34 TheWaytoReadDifferentTypesofStudy 35 TheWaytoReadDifferentTypesofStudy BiasinRCTs QuestionOne Whatwastheresearchandwhywasthestudyneeded QuestionTwo Whatwastheresearchdesign QuestionThree Wastheresearchdesignappropriatetotheresearchquestion Threepreliminaryquestions 36 EvaluateAPaperwithQuestions Doesthisnewresearchaddtotheliteratureinanyway Isthisstudybigger continuedforlongerorotherwisemoresubstantialthanthepreviousone Arethemethodsofthisstudyanymorerigorous Willthenumericalresultsofthisstudyaddsignificantlytoameta analysisofpreviousstudies Isthepopulationstudieddifferentinanyway e g differentethnicgroups agesorgenderthanpreviousstudies Istheclinicalissueaddressedofsufficientimportance anddoesthereexistsufficientdoubtinthemindsofthepublicorkeydecision makers tomakenewevidence politically desirableevenwhenitisnotstrictlyscientificallynecessary 37 EvaluateAPaperwithQuestions Specificquestions Whomisthestudyabout Ho