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Paula Peyrani, MD Instructor of Medicine Division of Infectious Diseases

Planning Your Study Observational Studies. Paula Peyrani, MD Instructor of Medicine Division of Infectious Diseases University of Louisville, Kentucky. Objectives. To describe the study design in observational studies. Planning The Study. Take a passive or active role in the study.

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Paula Peyrani, MD Instructor of Medicine Division of Infectious Diseases

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  1. Planning Your Study Observational Studies Paula Peyrani, MD Instructor of MedicineDivision of Infectious Diseases University of Louisville, Kentucky

  2. Objectives To describe the study design in observational studies.

  3. Planning The Study • Take a passive or active role in the study.

  4. Planning The Study • Take a passive or active role in the study.

  5. Planning The Study

  6. Planning The Study

  7. Planning The Study

  8. Planning The Study

  9. Planning The Study • No approach is better than the other.

  10. Planning The Study • No approach is better than the other. • Define which study is the best to answer the research question.

  11. Planning The Study • No approach is better than the other. • Define which study is the best to answer the research question. • Observational study may be a better choice or the only feasible option

  12. Clinical & Translational Research Study: Area/Problem/Question/Objective/Hypothesis Research Idea Streptococcus pneumoniae Beta lactam antibiotic (monotherapy) Beta lactam plus macrolides Clinical outcomes

  13. Planning The Study Cohort Studies Cohort: Roman term for a group of soldiers that marched together In clinical research, it is a group of subjects followed over time

  14. Planning The Study Cohort Studies Cohort: Roman term for a group of soldiers that marched together In clinical research, it is a group of subjects followed over time Study Subjects Time O

  15. Planning The Study Cohort Studies Cohort: Roman term for a group of soldiers that marched together In clinical research, it is a group of subjects followed over time Postmenopausal women Time Estrogen treatment

  16. Planning The Study Cohort Studies Cohort: Roman term for a group of soldiers that marched together In clinical research, it is a group of subjects followed over time • Describe the incidence or natural history of a condition.

  17. Planning The Study Cohort Studies Cohort: Roman term for a group of soldiers that marched together In clinical research, it is a group of subjects followed over time • Describe the incidence or natural history of a condition. • Analyze predictors (risk factors) for various outcomes.

  18. Planning The Study Cohort Studies Cohort: Roman term for a group of soldiers that marched together In clinical research, it is a group of subjects followed over time • Describe the incidence or natural history of a condition. • Analyze predictors (risk factors) for various outcomes. • Two basic variations: prospective or retrospective.

  19. Planning The Study Study Designs Hierarchy of Evidence Past vs. future outcomes Passive vs. active role Description vs. cause/effect 6 1. Case report/series 2. Cross-sectional study 3. Case-control study 4. Cohort study 5 Retrospective Study Observational Study Descriptive Study 4 3 2 1. Non-randomized 2. Randomized (RCT) Prospective Study Interventional Study Analytical Study 1 Retrospective Observational Descriptive Study Retrospective Observational Analytic Study Prospective Observational Analytic Study Prospective Randomized Clinical Trial

  20. Planning The Study Cohort Studies Descriptive study Postmenopausal women Time Estrogen treatment

  21. Planning The Study Cohort Studies Analytical study On estrogen Postmenopausal women Time CHD No estrogen

  22. Planning The Study Cohort Studies - Retrospective THE PAST THE PAST/PRESENT Population Risk factor present DiseaseNo disease Risk factor absent DiseaseNo disease Sample

  23. Planning The Study Cohort Studies - Retrospective THE PAST THE PAST/PRESENT HIV-infected subjects Normal vitamin D AIDS No AIDS Low vitamin D AIDS No AIDS HIV-infected subjects at UofL

  24. Planning The Study Cohort Studies - Retrospective Strengths - Good for investigating causes of a condition - Good for defining incidence - Measures variables completely and accurately - Much less costly and time consuming THE PRESENT THE FUTURE Postmenopausal Women Use of estrogens CHD No CHD No use of estrogens CHD No CHD Postmenopausal Women at UofL

  25. Planning The Study Cohort Studies - Retrospective StrengthsWeakness - Good for investigating causes of - Limited control over: a condition population sampling - Good for defining incidence quality of variables - Measures variables completely and accurately - Much less costly and time consuming THE PRESENT THE FUTURE Postmenopausal Women Use of estrogens CHD No CHD No use of estrogens CHD No CHD Postmenopausal Women at UofL

  26. Planning The Study Cohort Studies - Prospective THE PRESENT THE FUTURE Population Risk factor present DiseaseNo disease Risk factor absent DiseaseNo disease Sample

  27. Planning The Study Cohort Studies - Prospective THE PRESENT THE FUTURE Postmenopausal Women Use of estrogens CHD No CHD No use of estrogens CHD No CHD Postmenopausal Women at UofL

  28. Planning The Study Cohort Studies - Prospective Strengths - Good for defining incidence - Good for investigating causes of a condition - Measures variables completely and accurately THE PRESENT THE FUTURE Postmenopausal Women Use of estrogens CHD No CHD No use of estrogens CHD No CHD Postmenopausal Women at UofL

  29. Planning The Study Cohort Studies - Prospective StrengthsWeakness - Good for defining incidence - Inefficient way to study rare outcomes - Good for investigating causes of a condition - Measures variables completely and accurately THE PRESENT THE FUTURE Postmenopausal Women Use of estrogens CHD No CHD No use of estrogens CHD No CHD Postmenopausal Women at UofL

  30. Planning The Study Cross-sectional studies The investigator makes all measurements for each subject in a single occasion Subjects Time

  31. Planning The Study Cross-sectional study Population Risk factor; Risk factor; DiseaseNo Disease No risk factor; No risk factor; DiseaseNo Disease Sample

  32. Planning The Study Cross-sectional studies 100 women tested; 12 women diagnosed Subjects Time May

  33. Planning The Study Cross-sectional studies

  34. Planning The Study Cross-sectional studies

  35. Planning The Study Cross-sectional studies

  36. Planning The Study Cross-sectional studies

  37. Planning The Study Cross-sectional studies Strengths - No waiting for outcome to occur - Fast and inexpensive - No loss to follow-up

  38. Planning The Study Cross-sectional studies StrengthsWeakness - No waiting for outcome to occur - Difficult to establish causality - Fast and inexpensive - Impractical for the study of rare - No loss to follow-up diseases. - Limited information on prognosis and natural history

  39. Planning The Study Case-control Studies Study Subjects Time P O

  40. Planning The Study Case-control Studies P Study Subjects Time O

  41. Planning The Study Case-control Studies Cases Study Subjects Time P O Controls

  42. Planning The Study Case-control Studies Cases Study Subjects Time P Risk factors O Controls

  43. Planning The Study Case-control Studies THE PAST THE PAST/PRESENT Population with disease Sample with disease Risk factor present Risk factor absent Cases Sample with disease Larger population without disease Risk factor present Risk factor absent Controls

  44. Planning The Study Case-control Studies THE PAST THE PAST/PRESENT Prior abx use No prior abx use VAP due MDR Acinet to Prior abx use No prior abx use VAP due to suscep Acinet

  45. Planning The Study Case-control Studies THE PAST THE PRESENT Strengths - High yield of information from relatively few subjects - Efficient for diseases with long latent periods - Useful for generating hypothesis. Prior abx use No prior abx use VAP due MDR Acinet to Prior abx use No prior abx use VAP due to suscep Acinet

  46. Planning The Study Case-control Studies THE PAST THE PRESENT StrengthsWeakness - High yield of information from - Limited information relatively few subjects - Only one outcome can be studied - Efficient for diseases with long - Increased susceptibility to BIAS latent periods - Useful for generating hypothesis Prior abx use No prior abx use VAP due MDR Acinet to Prior abx use No prior abx use VAP due to suscep Acinet

  47. Planning The Study Case-control Studies THE PAST THE PRESENT StrengthsWeakness - High yield of information from - Limited information relatively few subjects - Only one outcome can be studied - Efficient for diseases with long - Increased susceptibility to BIAS latent periods - Useful for generating hypothesis Prior abx use No prior abx use VAP due MDR Acinet to Matching: Is a simple method of ensuring that cases and controls are comparable with respect to major factors that are related to the outcome but not of interest to the investigator Prior abx use No prior abx use VAP due to suscep Acinet

  48. Planning The Study

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