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Analytic studies

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The type of the study used for analysis and investigation of a relation between an exposure and outcome in the community.

The type of the study used for analysis and investigation of a relation between an exposure and outcome in the community.

Published in Health & Medicine
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  • 1. ANALYTIC STUDIES Prepared By: Dr.Anees AlSaadi CMT-P R4 December 2013
  • 2. ANALYTIC STUDIES • OUTLINE: – Hierarchy of Study design. – Introduction for analytic Studies./ Exposure & Outcome. – Cohort and Case control Study design: • Definition. • Character. • Advantages and disadvantages.
  • 3. ANALYTIC STUDIES Introduction
  • 4. ANALYTIC STUDIES Introduction: Testing specific hypotheses. Samples of subjects are identified and information about exposure status and outcome is collected.
  • 5. ANALYTIC STUDIES Introduction: Groups of subjects are compared in order to estimate the magnitude of association between exposures and outcomes.
  • 6. ANALYTIC STUDIES Introduction: The two main types: Cohort study Case-control study
  • 7. ANALYTIC STUDIES Introduction: Exposure Outcome
  • 8. ANALYTIC STUDIES Cohort study: Exposure Outcome
  • 9. ANALYTIC STUDIES Cohort study: Definition
  • 10. ANALYTIC STUDIES Cohort study: Definition
  • 11. ANALYTIC STUDIES Cohort study: Definition Is an analytic epidemiologic research design in .which the study population is composed of individuals who are classified as exposed and no exposed to particular risk factors. These groups are followed forward for a specific period of time to estimate the incidence rate of an outcome or the development of a health problem.
  • 12. ANALYTIC STUDIES Non Exposed Group Hypothesized to be at greater risk or lesser risk of developing the health problem Exposed Group Cohort study: Already exposed. Casual factors Protective factors Not exposed Protective factors Casual factors
  • 13. ANALYTIC STUDIES Cohort study: What is the Potential Source of Study Subjects…… ?
  • 14. ANALYTIC STUDIES Cohort study: Developing problem. Not developing problem. Death. Study Subjects in Each Groups followed in same manner. Lost to follow up. Study Ends.
  • 15. ANALYTIC STUDIES Cohort study: Cohort study Prospective Historical Exposure status is determined when the study begins. Followed forward in time to observe the outcome. The exposure happened before the study begins.
  • 16. ANALYTIC STUDIES Cohort study: Example
  • 17. ANALYTIC STUDIES Cohort study: The most important bias is loss of follow ups (drop out).
  • 18. ANALYTIC STUDIES Cohort study: • • • • • • Advantages: More control on data collection. Easy checking the study outcome. Clear temporal sequence. Estimating the risk. Good to study rare risk factors. Can study different disease or outcomes. Disadvantages: • Only risk factors defined at the beginning of the study can be studied. • Costly. • Time consuming. • For common diseases. • The exposure status may change during the study. • Loss of follow up.
  • 19. ANALYTIC STUDIES Case Control Study: Definition It is analytic type of epidemiologic research design in which the study population consists of groups who either have (cases) or do not have (controls) a particular health problem or outcome.
  • 20. ANALYTIC STUDIES Case Control Study:
  • 21. ANALYTIC STUDIES Case Control Study: The investigator selects the case and the control group on the bases of the outcome and compares them in term of their frequency of past exposure to the possible exposure.
  • 22. ANALYTIC STUDIES Case Control Study: Retrospective Study
  • 23. ANALYTIC STUDIES Case Control Study: Cases Controls
  • 24. ANALYTIC STUDIES Case Control Study: Cases Study subjects who have outcome to be investigated. Case definition: Objective description of the case. Eligibility Criteria. Controls Study subjects who do not have the outcome to be investigated. Similar to the cases in most of the aspects except outcome. Sources: Hospital Community
  • 25. ANALYTIC STUDIES Case Control Study:
  • 26. ANALYTIC STUDIES Case Control Study: Controls Cases Similarity
  • 27. ANALYTIC STUDIES Case Control Study: • Selection of controls: – No outcome. – Selection randomly or Systematic. – Matching on specific variables./individual or frequency. – Restriction.
  • 28. ANALYTIC STUDIES Case Control Study: What is the Potential Source of Study Subjects…… ?
  • 29. ANALYTIC STUDIES Case Control Study: The most important bias is recall .
  • 30. ANALYTIC STUDIES Case Control Study: • • • • • • Advantages: Quick design saves time. Easy to perform. Inexpensive. Suitable for rare diseases. Can study many risk factors. Useful for generating hypothesis. Disadvantages • • • • Recall bias. Can not be used for incidence rate. Temporal relationship. Can study only one disease outcome. • Can only obtain relative measure of risk.
  • 31. Practical Exercise