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RSS study design


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Research Summer School - Study designs - Dr. Nisreen Jastaniah

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RSS study design

  1. 1. 06/15/131Dr. Nisreen A. JastaniahAssist Prof KSAU-HSConsultant Geriatric Medicine KAMC-JTypes Of Epidemiological StudiesTypes Of Epidemiological Studies(Study Design)(Study Design)
  2. 2. Study DesignResearch :Diligent inquiry or examination in seeking facts.Laborious or continued search after the truth.Systematic investigation towards increasing the sum ofknowledge.An endeavour to discover new or collect old facts bythe scientific study of a subject or by a course ofcritical investigation.
  3. 3. Study DesignStudy design:Is the master plan specifying the methods and proceduresfor collecting and analyzing the needed information.The choice of the most appropriate design dependslargely on the objectives
  4. 4. Study DesignQuestion –Related- (P patient , I intervention ,C comparison group , O outcome , T time )F feasibleI interestingN novelE ethicalR relevant
  5. 5. Study designLongitudinalDescriptiveCross sectionalCase reportCase seriesInterventional(RCT)ObservationalCase-controlCohortStudy DesignStudy Design
  6. 6. Study DesignStudy Design DescriptiveDescriptive(Cross sectional)(Cross sectional)Qualitative studyA qualitative study explores people’s subjectiveunderstandings of their life and experiences.Methods used include– Direct observation– Interviews– The analysis of texts or documents or recordedspeech or behavior
  7. 7. Study DesignStudy Design DescriptiveDescriptive(Cross sectional)(Cross sectional)Qualitative studiesAdvantages• Obtain views, opinions and perspectives ofindividuals included in the study• Identify themes that could may not been identifiedfrom a quantitative studyDisadvantages• Generalizabiltiy
  8. 8. Study DesignStudy Design DescriptiveDescriptive(Cross sectional)(Cross sectional)
  9. 9. Study DesignStudy Design DescriptiveDescriptive(Cross sectional)(Cross sectional)
  10. 10. Study DesignStudy Design DescriptiveDescriptiveCASE EPORT/SERIESCASE EPORT/SERIESCASE REPORT/SERIESDescribe patients’ characteristics, and may generate ideas for future studies
  11. 11. Study DesignStudy Design DescriptiveDescriptiveCASE REPORT/SERIESCASE REPORT/SERIESAdvantages• Useful when the disease is uncommon• First to provide clues to identify a new disease oradverse effectDisadvantages• Usually small sample size• Only of minor relevance to public health
  12. 12. Study DesignStudy Design DescriptiveDescriptiveCASE REPORT/SERIESCASE REPORT/SERIES
  13. 13. Study DesignStudy Design Longitudinal-observationalLongitudinal-observationalCase-control studyCase-control studyDiseaseNo disease(control)YesNoYesNoStarting pointHistory of exposureCompare & draw conclusions
  14. 14. Study DesignStudy Design Longitudinal -ObservationalLongitudinal -ObservationalCase-control studyCase-control studyAdvantages ofcase – control studies Quick Require reasonably small numbers Reasonably economical Sensible for study of rare diseases No loss to follow – up Can test current hypotheses
  15. 15. Study DesignStudy Design Longitudinal - observationalLongitudinal - observationalCase-control studyCase-control studyDisadvantages of case – control studies Uncertain if exposure preceded disease Potential for recall bias (sick people may be more [or less]likely to recall exposure) Selection bias (recruitment influenced by exposure)
  16. 16. Longitudinal - observationalLongitudinal - observationalCase-control studyCase-control study
  17. 17. Longitudinal – ObservationalLongitudinal – ObservationalExposedNot exposed(control)YesNo YesNoDiseaseFollow upStarting pointCompare & draw conclusionsCohort studies
  18. 18. Longitudinal – ObservationalLongitudinal – ObservationalCohort StudiesCohort StudiesAdvantages of Cohort Study• Can collect exposure information as exposurehappens• Can collect multiple different exposures• Exposure information should be relativelyreliable• Can collect information as outcome happens
  19. 19. Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort StudiesDisadvantages of cohort studies• Duration of study: may take decades to complete• Subjects must be followed over time• Cost: very expensiveCan you afford to wait decades for your answer?
  20. 20. Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies
  21. 21. Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies
  22. 22. Longitudinal – ObservationalLongitudinal – Observational
  23. 23. Study Design & Evidence Based Clinical PracticeStudy Design & Evidence Based Clinical PracticeDifferent questions study designPrevalence or frequency of factor Cross sectionalHypotheses about possible Harm (or causes) Case-controlHarm or Causes or risk factors CohortExperience of illness QualitativeEffectiveness RCT
  24. 24. Experimental Study DesignStudy designLongitudinalDescriptiveCross sectionalCase reportCase seriesinterventionalobservationalCase-controlcohort
  25. 25. Experimental Study DesignA type of research that tests how well new medicalapproaches work in people. These studies test newmethods of screening, prevention, diagnosis, ortreatment of a disease.
  26. 26. Experimental Study Designcontrolled clinical trialA clinical study that includes a comparison (control) group. Thecomparison group receives a placebo, another treatment, or notreatment at all.
  27. 27. Experimental Study Design Clinical trialsampleinterventioncontrolYesNo YesNoinclusionexclusionimproved
  28. 28. Experimental study designExclusion criteriaBe parsimoniousCompelling (clinicalcharacteristics).(?follow-up , compliance , highrisk).Inclusion CriteriaBe specificSpecify populations relevant tostudy question(Demographic , Geographic ,clinical characteristics).
  29. 29. Experimental Study DesignRandom AssignmentComparable groups(Treatment & Control)confounding variableIs a variable in a onegroup that correlate(positively ornegatively) with theoutcomeSampleI CRandom Allocation
  30. 30. Experimental Study Designintervention group (I)The group receiving the study agent thatis being tested in a clinical trial orclinical studyControl group:In a clinical trial, the group that does notreceive the new treatment beingstudied.
  31. 31. Experimental Study DesignBlinding;Eliminates unintentional prejudices bythose involved…honest answers(Single blind , double blind)both the patients and the research staff donot know and cannot figure out whichpatients are receiving treatment andwhich placebo.Co-intervention & contaminationBlindCo-interventionI C
  32. 32. Experimental Study DesignSI CDrop-outDropoutThe loss of participants during thecourse of a study. (Also called loss tofollow up.)more than 20 percentIntention to treat
  33. 33. Experimental Study DesignDisadvantageMost costly & time consumingRandomization, blinding, placebos…Not feasible for outcomes that arerare or have long lag timesSample may be very restrictivemaking extrapolation difficultAdvantagePotential for bias & confounding istheoretically eliminatedBest design to establish cause & effect
  34. 34. Good Work …. Team WorkChoose mentor wiselyGet an epidemiologist / statistician
  35. 35. Study DesignStudy designLongitudinalDescriptiveCross sectionalCase reportCase seriesinterventionalobservationalCase-controlcohort
  36. 36. 15/06/1338
  37. 37. ThankYou