Research Methods: Introduction To Epidemiology Operational Studies In .
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSResearch Methods:Introduction to EpidemiologyOperational Studies in TuberculosisMichael Lauzardo, MDPrincipal Investigator, Southeastern National Tuberculosis CenterCenterAssistant Professor, Division of Pulmonary and Critical Care Medicine,Medicine,University of Florida College of MedicineDeputy Health Officer for TB – State of FloridaEpidemiologyThe Public Health Cycley Is the process to study the distribution and determinants of diseasefrequencyMeasure/EvaluateEpidemiologyy Is a discipline which approaches problems systematically andquantitativelyAnalyzeEpidemiologyInterveney Is the basic science of public healthCommunicateEpidemiologyHistory of Epidemiologyy Disease frequency (descriptive):y Original focus was infectious disease epidemicsy Quantifies the occurrence of disease[How many?]many?]y Current epidemiology is much broader– Acute and chronic diseases– Health events– Conditions– Behaviorsy Disease distribution (descriptive):y Who gets the disease? Where is the disease occurring? When is thedisease occurring?y Disease determinants (analytic):y Combination of first two (Why?(Why?))PAGE 1
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSPopulationsThe Epidemiologist’Epidemiologist’s Toolboxy Experimental Studiesy Unit of observation is groups rather than individuals– Investigators allocate the exposurey Clinical observations and basic science inform epidemiology, butepidemiology also informs clinical practicey Observational Studies– Investigators observe natural course of events– Understanding disease trends helps clinical providers withtheir diagnosesA Typical Epidemiological Approach (1)A Typical Epidemiological Approach (2)y Assess validity of any observed associationy Determine the existence and magnitude of a problem– Exclude possible alternative explanationsyyyy Describe who has the problem:– Person, place, and timey Develop hypotheses about why the problem occursChanceBias - systematic data collection/interpretation errorConfounding - other variables cause the observed associationy Make judgement if a true causecause-effect relationship exists between factor andoutcomey Test these hypotheses using appropriate analytic study designs andandstatistical techniquesy Based on the findings, develop interventionsy Evaluate intervention effectivenessImportant Definitionsy Risk:Risk: the statistical chance of being ill if one is exposed to somefactory Exposure:Exposure: being in contact with, or having, a factor which may ormay not be the cause of illnessRatios, Proportions, and Rates[other term used risk factor]factor]PAGE 2
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSProportionsRatiosy Proportion a ratio in which the numerator is included in denominator,often expressed as %– e.g. 4/100 homeless individuals have TB 4%y Express the relationship of two quantities. These quantitiesmay be related or totally independent– x / (x y) or x / yy Prevalence proportion of individuals in a population who have the diseasedisease(event)y Example: A hospital sees 4000 male TB patients and 2000female TB patients.– The ratio of male to female TB patients 4000 / 2000 2 / 1 2 to 1– Point prevalence: # with disease / total # in population at a given pointin time– Period prevalence: # with disease any time during a given interval /total # in population at midmid-intervalRatesComparison of Incidence and Prevalencey A ratio with a distinct relationship between the numerator &denominator, and time is an intrinsic part of the denominatory Prevalence Incidence X Duration of illnessy Incidence quantifies the # of new events or cases of disease thatdevelop in a population at risk during a specified time intervaly Prevalence is the product of incidence and disease duration– Example:South Africa had 346 new TB cases per 100,000 population in 2000Incidence RatesOther Important Ratesy Morbidity: measure rate of illness/ timey Cumulative incidence rate # new cases during specified time period /total pop at risk at midmid-interval[note: assumes everyone in study for whole time period]y Mortality: measure rate of death/ time– Crude mortality rate:rate: the mortality rate from all causes of death for a specifiedpopulationy Incidence density rate # new cases during specified time period / totalpersonperson-time atat-risk[note: accounts for different amounts of time in study]– CauseCause-specific mortality rate:rate: the mortality rate from a specified cause for aspecified population– AgeAge-specific mortality rate:rate: a mortality rate which limits both the numeratorand denominator to a particular age or age groupPAGE 3
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSEstimated Annual Incidence of TB in High BurdenCountries, 1999PopulationRate x105 (thousands)Country1. India2. China7. Philippines8. S. Africa10. Viet Nam13. Brazil15. 71,300234197149118123Risk Ratio or Relative RiskAll Roads Lead to Ratiosy The ratio of two ratiosy Proportions, such as PREVALENCE,PREVALENCE, and Rates, such asINCIDENCE,INCIDENCE, are both specific types of ratiosy A way to compare risks in those exposed versus those not exposed– If 4 in 100 people who are homeless develop TB (exposure homeless),(exposure homeless),then risk 4/100 0.04 4%– If 1 in 100 who are not homeless develop TB, then risk 1/100 0.01 1%y RELATIVE RISKS and ODDS RATIOS (to be discussed morelater later ) are ratios of ratios– Then the risk ratio is 4/100 divided by 1/100 4/1– Homeless people are 4 times more likely to get TB as nonnon-homelessConclusiony Epidemiology– Is a basic tool for public health action– Provides data for decisiondecision-makers– Increasingly emphasizes development and evaluation ofcontrol measuresStudy Designy Application of findings to improve healthPAGE 4
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSStudy TypesQuestions for Study Designy What is the purpose?y Descriptive studiesy What information is needed to intervene?y When is it needed?y Analytical studiesy What kind of study provides the answers?– Experimental– ObservationalDescriptive Studies: Person (1)Descriptive Studiesy Question: Who is getting the disease/event?y Describes patterns of diseasey Characteristics of person must include age and sex– person, place, timey Other characteristicsy Provides data for program planning– high risk behaviors: alcohol use, smokingy Provides data for resource allocation– Homelessness, incarceration, income level, occupation, or othersy Generates hypothesesDescriptive Studies: Person (2)Descriptive Studies: Person (2)Death Rates per 100,000 from coronary disease in theUS, 1981, by age and sexDeath Rates per 100,000 from coronary disease in theUS, 1981, by age and 4708.7243.76565-741669.9769.46565-741669.9769.475 5696.04215.175 5696.04215.1PAGE 5
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSEstimated Percent of New Cases thatare MDR-TB, 2000Descriptive Studies: Place (1)y Question: Where are the rates of the disease highest and lowest? Wheredo resources need to be targeted?y Geographic characteristics can provide insights into disease etiologyetiologyy Geographic comparisons of disease frequency can be madey Data can be efficiently presented in a pictorial manner0 - 0.91 - 2.93 - 4.95 - 6.97 or moreNo EstimateTuberculosis Morbidity in RussiaDescriptive Studies: Time (1)per 100,000 population80y Question: When does the disease (event) occur? Is the diseasefrequency different now compared to the past?y Changes in disease rates over time can signal an epidemic orintroduction of the causal agenty Cyclic changes, such as seasonal patterns, are very 198419861988199019921994199619980Descriptive Studies:Correlational (Ecological)Descriptive Studies: Typesy Correlational studiesy Determines the relationship of disease and exposure in a populationpopulationy Case Reports and Case Series– Different groups, same time periody CrossCross-sectional Surveys– Same group, different time periody Cannot link an exposure to the occurrence of disease in the individualindividualPAGE 6
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSPrimary MDR TB in USUS-born versus ForeignForeign-bornPersons, 19931993-2001Descriptive Studies:Case Reports and Case Seriesy Careful, detailed report(s)report(s) by one or more cliniciansy No denominator% newTBcasesDescriptive StudiesCrossCross-sectional StudySummary:Descriptive Studiesy Both exposure and disease outcome is measuredsimultaneouslyy Characterize disease by person, place, timey Generally used to determine association between disease andexposurey Assist in generating hypothesis, but not used to test hypothesisy Three types: Correlational,Correlational, case reports or case series, crosscross-sectionaly Usually cannot establish if exposure came before or afterStudy TypesAnalytic Studies (1)y Descriptive studiesy Used to test epidemiologic hypothesesy Identify risk factorsy Analytical studiesy Compare groups– Observational– Experimental or InterventionPAGE 7
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSAnalytic Studies (2)Analytic Studies:CaseCase-Control Studyy Observational Studies– Investigators observe natural course of events– Two typesy Subjects are selected on basis of outcome status– Case: Subject with outcome of interest– Control: Subject without outcome of interest in the samepopulationy Exposure for two groups is determinedy CaseCase-Control Studyy Cohort Studyy Experimental Studies– Investigators control the exposureEXPOSUREBasic Analytical Approach in aCase-Control StudyOUTCOMEBasic Analytical Approach in aCase-Control StudyTotal populationTotal olsControlsNon-ExposedBasic Analytical Approach in aCase-Control StudyBasic Analytical Approach in aCase-Control StudyTotal populationTotal sedNon-ExposedOdds osedNon-ExposedPAGE 8
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSAdvantages and Disadvantages(1):CaseCase-ControlExample: CaseCase-Control Studyy “Smoking and mortality from TB and other diseases in India:retrospective study of 43,000 adult male deaths and 35,000controls,”controls,” Gajalakshmi et aly Advantages– Best design for rare outcome– Can identify more than one exposure– Cases: men who died of disease– Relatively quick and inexpensive– Controls: living men– Exposure: SmokingAdvantages and Disadvantages(2):CaseCase-ControlAnalytic Studies:Cohort Studyy Disadvantages– Not useful for rare exposures– Not populationpopulation-based, cannot calculate incidence rates of disease– Time relationship between exposure and disease may be difficultto establish– Prone to selection and recall bias– Hard to ascertain exposure accuratelyy Subjects are chosen on the basis of the presence or absenceof exposurey Subjects are followed for a specified period of time todetermine the development of outcomeEXPOSUREAnalytic Studies:Cohort Study TimingAnalytic Studies:Cohort Study Timingy Prospective: Subjects followed from time of exposure (present)to outcome (future)ExposurePastPresent(initiation of study)OUTCOMEy Retrospective: Exposure and outcome occurred in the t(initiation of study)TimelinePAGE 9Future
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSBasic Analytical Approach in aCohort StudyBasic Analytical Approach in aCohort StudyTotal populationTotal populationExposedExposedOutcomeNo OutcomeOutcomeNon-ExposedNon-ExposedNo outcomeBasic Analytical Approach in aCohort StudyBasic Analytical Approach in aCohort StudyTotal populationTotal populationOutcomeExposedOutcomeIncidenceExposedNo OutcomeIncidenceNo OutcomeRelative o outcomeIncidenceNo outcomeAdvantages and Disadvantages:Cohort (1)Example: Cohort Studyy Advantagesy “Effect of Highly Active Antirntiretroviral Therapy (HAART) on incidence oftuberculosis in South Africa: a cohort study,”study,” Badri et al– Exposed: HIV patients receiving HAART– Unexposed: HIV patients without HAART– Outcome: active TB– Best design for studying common diseases or rare exposures– Can examine multiple outcomes– Can determine time relationship between exposure and outcome– Can measure incidence of outcomePAGE 10
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSAnalytic Studies Experimental/Intervention StudyAdvantages and Disadvantages:Cohort (2)y Disadvantagesy Type of cohort (ex: clinical trial)y Exposure status is determined by the investigatory Provides the most reliable evidence from epidemiologicresearch– randomization used to determine exposure statusy Ethical issuesy Expensive– Is inefficient for rare diseases– Can be expensive and timetime-consuming– Validity of the results can be seriously affected by losses tofollowfollow-up– Requires the availability of adequate records if retrospectiveDesign ChoiceConclusiony Descriptive studies describe patterns of disease occurrenceand allow the formulation of hypothesesy The choice of study design to use for a particular exposureexposureoutcome relationship depends upon– The nature of the outcome under investigationy Analytic studies generally test epidemiologic hypotheses– The type of exposurey For most epidemiologic hypotheses, it is necessary anddesirable to employ both descriptive and analytic designstrategies– The available resourcesSteps in the research processyyyyyyyyWriting a Research ProposalPAGE 11Generate a research questionOrganize a teamDraft a proposal/protocolGet TB Program and ethics approvalTest on a small scale (pilot) and revise proposalDo study and analyze dataMake conclusions for report and manuscriptDisseminate information and plan action
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSA good proposal proposal Why write a proposal?y Focuses on a clear and specific research questiony To organize your own thinking and plansy Uses a structured formaty To share your ideasy Is easy to read and understand– Why,Why, what,what, and how you want to do somethingy Is detailed enough so any reader can understandy To ask for fundsy Anticipates most questions and problemsy To obtain ethical clearanceA good proposalA proposal starts with an importantideay Allows planningy A problemy Helps secure support from supervisors and fundersy Makes doing the activity easyy Makes doing the analysis easiery A questiony Makes drawing conclusions easiery Makes writing the report easiery A hypothesis– Cause EffectComponents of a proposalExamples of TB research questions1. Background/Rationale2. Objectives and hypothesis3. Methods4. Ethics/Protection of human subjects5. Timeline6. Budget7. Investigators and responsibilities8. Results dissemination9. Appendicesy Why do patients interrupt TB treatment?y Why do TB drug shortages occur at district clinics?y Does treatment failure predict MDR TB?y What kind of stigma is attached to TB?y Is clinicclinic-based DOT more costcost-effective than homehome-basedDOT?PAGE 12
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSBackground: Componentsy General background of issuey Literature review and previous data1. BACKGROUND/ RATIONALE– Has anyone studied this question before?– If yes, are the answers relevant?y Is it ethical to do it again? (Use of resources)y Is it essential to do it again? (Justification) Why is it important to do this study?– What will THIS study contribute?y What is the funding source?y What is the intended use of the findings?Sources of informationy PeerPeer-reviewed books and articles, official statistics (best)– Lancet, New England Journal of Medicine, JAMA, WHOBulletin, PanAmerican Journal of Public Health, InternationalJournal of TB and Lung Disease, etc.2. OBJECTIVES AND HYPOTHESISy Health services reports (good) What is the purpose of this study?y Personal communications/anecdotal evidence (fair)Objectives and hypothesisObjectives: Examplesy Objectives– Measure body mass changes in children on TB treatmentin district X in 2004– Identify the barriers to clinic access by TB patients in ruralareas in 2004– Compare the treatment outcomes of male and femalepatients at health centre Y during 2003– Determine whether previous TB treatment is a risk factorfor antianti-TB drug resistance– Compare the cost to society of homehome-based and clinicclinicbased DOT in province Z– Statement of what you will do, short and clear– May be primary and secondary objectives– Must be specific and attainabley Hypothesis:– Cause Effect– Concise, clear, specificPAGE 13
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSMETHODS Components3. METHODSDesignInterventionStudy populationStudy sampleEnrollment proceduresData collection and variablesData analysisLimitationsPilot studyTraining “ “How are you going to do the study?”study?” “ “Who are you studying?”studying?” “ “When will you do the study”study”3.1 Design3.2 Intervention(s)Intervention(s)yyyyyy Descriptive study?y Analytical study? (Asking WHY?)– CrossCross-sectional– CaseCase-controlRefers to the intervention received by the study participantsMay have been administered in the past (retrospective study)Can be more than one per study (describe all)One can be the common standard of care, or no careDescription must be detailed enough– Cohorty Is it testing an intervention?– Randomized controlled trialy Prospective or retrospective?Intervention: Example3.3 Study Population“The antianti-TB drug regimens used in Country A and referred to in thisstudy, are defined as follows:– Standardized treatment for MDRMDR-TB: Three months of PZA,EMB, ethionamide,ethionamide, kanamycin, and ciprofloxacin, followed with15 months of PZA, EMB, ethionamide,ethionamide, and kanamycin.Treatment is administered daily and under direct observation.– Individualized treatment for MDRMDR-TB: A treatment regimen of atleast 18 months duration that includes at least five drugs, towhich the organism has shown in vitro susceptibility. It isadministered daily under direct observation.”observation.”y Exactly WHO will be studied– Time, place, persony Inclusion & exclusion criteria– Stated exclusions – eg children, recent arrivals, prisoners,extrapulmonary TBPAGE 14
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODSInclusion and exclusion: ExampleStudy Population: ExampleParticipants Inclusion Criteriay Patients who started treatment with secondsecond-line drugs between August 1996 andMarch 2002. Patients with HIV disease, a history of renal insufficiency,insufficiency, hepatitis, ordiabetes will be analyzed separately due to these medically complicatingcomplicating factors.Participant Exclusion Criteriay Children 18 years old, pregnant women, and/or those for whom treatmentoutcomes cannot be determined with certainty.Justification of Exclusiony Establishing a cultureculture-confirmed treatment outcome for children is much more difficultthan for adults. As this evaluation relies on knowing treatment outcomes, childrenhave been excluded. Lastly, MDRMDR-TB treatment and MDRMDR-TB treatment outcomes aremore complex for pregnant women, and thus pregnant women have beenbeen excludedfrom this evaluation.Estimated Number of Participants: 2700“The study population is made up of adult TB patients in CountryA who began treatment for MDRMDR-TB between August 1996 andMarch 2002. These patients are distributed throughout Country A,however a majority of them are residents of the capital.3.4 Case DefinitionCase Definition: Exampley Criteria for classifying subjects as cases or controlsy Does not need to be a TB case (depends on the study question)y For the purposes of this study, a patient who receivedMDRMDR-TB treatment is a patient who was enrolled in asecondsecond-line drug regimen for at least 1 day.3.5 Study Sample3.6 Participant enrollmenty Describe the sampling framey How will eligible participants be identified– E.g.: clinic’clinic’s patient registryy Will study participants be assigned a study ID number?y Describe the sampling methody Who will talk to the eligible participants to ask them toparticipate?– Random, systematic, cluster, etc.y Stratification?y Will a form be filled at the time of enrollment?y Indicate the sample Size (n xx)– Computer, table, formula, or statistician– Based on estimated proportion of what is being measured,precision and variation requiredPAGE 15
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODS3.7 VariablesVariables : Examplesy List each variable necessary for the analysisy SocioSocio-demographic characteristics– Gender, age, etc.– Dependent, independent, control control y Culture dates and resultsy Describe what it will look like and how it will be created––––y Treatment outcomesType (dummy, index, scale, categorical, etc.)ValuesSource of informationAny recoding, calculations involved, etc.y Drug expiry datesy Distance between patient’patient’s house and clinicy Number of patients per DOT workery Patient’Patient’s accurate knowledge of TB transmissiony Quality of TB services at clinicsSources of data3.8 Data collectiony Recordsy Design questionnaire/data collection formsy Describe the data collection process– Patient histories, lab registry, personnel roll, etc.– Who will collect/abstract the data?– How many data collectors?– Who will supervise the data collection?y Interviews or surveysy Observationsy Tests/instrumentsy Describe data entry process– Who will enter the data?– Software used?– How will the data quality be checked?3.9 Data analysis plan3.10 Limitationsy Software usedy Description of bias you might expect– SelfSelf-report biasy Statistical approach– Univariate – frequencies– Bivariate – x by y tables– Multivariate (regression)– Recall bias– LagLag-time bias– Selection biasy Limitations in design that you cannot fixy Planned tables and figuresy Can you estimate true cause - effect?Refer to objectivesand research question!PAGE 16
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODS3.11 Pilot Study3.12 Trainingy Purpose of trainingy Purpose: to check study procedures:–––––y Who will be trained, by whomUnderstanding (survey questions)AcceptabilityFeasibilityTime, distancesFurther training needsy What you will train them to doy When training will occury Where training will take placey Describe where, when and how pilot testing will occurInformed consent4. HUMAN SUBJECTS PROTECTIONy Describe all measures taken to protect study participants fromharmy Needed for research with human subjectsy Must follow three principles– Describe possible harm – pain, risks, embarrassment, costs,costs & risks to health services– Participation is voluntary– Participant must be able to understand the purpose ofthe research, in language that is understandable– (How) will informed consent be obtained?– How will confidentiality/privacy be protected– Participation must NOT be coerced– What will be done if a problem arisesExamples of protective measuresConsent Form: Essential ComponentsyyyyyyyyyyyyyDescribe nature of research and proceduresDescribe nature and duration of participationRisk & benefits (physical, psychological, social)Stress that participation is voluntaryMust state that the participant can stop taking part at any timeDescribe how you will protect confidentialityName of contact who can answer questions about the studyPAGE 17Writing consent forms in simple languageTranslate consent forms into participants’participants’ native languageNot writing patients’patients’ name on data collection formsKeeping filled forms in locked cabinetsDestroy pages containing identifiers once data is enteredTraining data collectors to maintain confidentiality
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODS5. TIMELINETIMELINE Continuedy Work back from deadliney Proposal writingMonth 11-2y Recruiting, training of fieldworkers & pilotingMonth 3y Finalizing interview formatMonth 3y Permission, ethicalclearance, fundingMonth 5y Data collectiony Data collectionMonth 66-8y Data entry & cleaningMonth 8, 9y AnalysisMonth 9, 10y Report writingMonth 11y Deadline for reportMonth 12y Community meetingsMonth 1212-14y Conference presentationMonth 1212-14Month 66-86. BUDGETBUDGET Continuedy Stationary, photocopies, printingy What resources will be needed to conduct the study?y Salaries: Different personnel categoriesy Telephones, faxes, couriers, postage– (Amount) x (duration) Totalyyyyy Report disseminationTraining (equipment, space, refreshments, etc.)Travel (airfare, bus fare, hotel, perper-diem)Office accommodation and furnitureEquipment (computer, printer, software)y Writteny Conference attendancey Community meetings – hire of hall, refreshmentsy Administrative charges8. RESULTS DISSEMINATION7. INVESTIGATORS and RESPONSIBILITIESy Name, title, affiliation To whom will results be reported?y Contact information for each Unethical NOT to report research (whatever the results) Variety of forums– Address, phone, fax, ee-maily Describe in detail who will do what conference, publication, report, community meetingPAGE 18
2008 HEALTH RESEARCH IN THE AMERICAS IV: HIV/TBMODULE 1: RESEARCH METHODS9. APPENDICESy Information sheet and consent formy Data collection instrument(s)instrument(s)Conclusiony Other relevant documentsPAGE 19
Introduction to Epidemiology Epidemiology yIs the process to study the distribution and determinants of disease frequency yIs a discipline which approaches problems systematically and quantitatively yIs the basic science of public health The Public Health Cycle Measure/Evaluate Epidemiology Analyze Epidemiology Communicate Intervene Epidemiology
Introduction to Genetic Epidemiology Different faces of genetic epidemiology K Van Steen 2 DIFFERENT FACES OF GENETIC EPIDEMIOLOGY 1 Basic epidemiology . Clayton D. Introduction to genetics (course slides Bristol 2003) Bon
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Step-by-step learning in playing and reading, starting from absolute scratch Performance pieces in a range of styles from classical and folk through to jazz A helpful and stimulating CD with recordings of the pieces together with many ‘play-along’ tracks and aural development exercises Explanation of music theory Warm-up exercises Even more performance pieces for each .
