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Introduction to Clinical Research Methodology

Introduction to Clinical Research Methodology. Introduction Overview of the Scientific Method Criteria Supporting the Causal Nature of an Association Outline of Available Research Designs. From The Book of Daniel, Chapter One.

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Introduction to Clinical Research Methodology

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  1. Introduction to ClinicalResearch Methodology • Introduction • Overview of the Scientific Method • Criteria Supporting the Causal Nature of an Association • Outline of Available Research Designs

  2. From The Book of Daniel, Chapter One 12 Try thy servants, I beseech thee, ten days; and let them give us pulse (leguminous plants) to eat and water to drink... 13 Then let our countenances be looked upon before thee; and the countenances of the youths who eat of the king’s food... 14 So, he harkened unto them and tried them in this matter, and tried them ten days... 15 And at the end of ten days their countenances appeared fairer, and they were fatter in the flesh, than all of the youths that did eat of the king’s food.

  3. Galen, Second Century All who drink of this remedy recover in a short time, except those whom it does not help, who all die. Therefore it is obvious that it fails only in incurable cases.

  4. Lind’s Treatise on Scurvy, Part 1 ... I took twelve patients... (with) scurvy... Their cases were as similar as I could have them... They lay together in one place and had one diet common to all. Two of these were ordered each a quart of cyder a day. Two others took twenty-five drops of elixir of vitriol three times a day upon an empty stomach. Two others took two spoonfuls of vinegar three times a day... Two of the worst patients were put upon a course of seawater. Of this they drank half a pint very day. Two others had each two oranges and one lemon given them every day. C.P. Stewart and D. Guthrie, Eds. Edinburgh University Press, 1953.

  5. Lind’s Treatise on Scurvy, Part 2 The two remaining patients took an electuary recovered by a hospital surgeon made of garlic, mustard, balsam of peru and myrrh. The consequence was that the most sudden and visible good effects were perceived from the use of oranges and lemons; one of those who had taken them being at the end of six days fit for duty. The other was the best recovered of any in his condition and was appointed nurse to the rest of the sick. C.P. Stewart and D. Guthrie, Eds. Edinburgh University Press, 1953.

  6. Definition: Epidemiology • Epidemiology is the study of the distribution and determinants of health and disease in populations, and is the basic science underlying much of public health and preventive medicine.

  7. Definition: Clinical Epidemiology • Clinical Epidemiology extends the principles of epidemiology to the critical evaluation of diagnostic and therapeutic modalities in clinical practice.

  8. Definition: Biostatistics • Biostatistics is concerned with the development of statistical theory and methods, and their application to the biomedical sciences.

  9. Types of Associations between Factors Under Study • None (independent) • Artifactual association (spurious or false association) • Chance (unsystemic variation) • Bias (systematic variation) • Indirect association • Causal association (direct association)

  10. Overview of the Scientific Method Study Sample Statistical Inference Conclusion About a Population(Association) Biological Inference Conclusion About Scientific Theory(Causation)

  11. Criteria Supporting the Causal Nature of an Association • Coherence with existing information • Time sequence • Specificity • Consistency • Strength • Quantitative strength • Dose-response relationship • Study design

  12. Options in Research Design • Analytic Studies • Experimental Study • Prospective Cohort Study • Retrospective Cohort Study • Case-Control Study • Descriptive Studies • Analyses of Secular Trends • Case Series • Case Reports

  13. Case Report • Definition • A clinical description of a single patient • Use • Hypothesis generation • Limitation • Generalizability - patient may be atypical

  14. Case Series • Definition • A clinical description of a number of patients with a disease • Use • Characterization of the illness • Limitation • No control group: cannot determine which factors in the description are unique to the illness.

  15. Analysis of Secular Trends • Definition • A study comparing geographic and/or time trends of an illness to trends in risk factors • Use • Rapid and easy support for or disproof of hypotheses • Limitation • Cannot differentiate among those hypotheses consistent with the data

  16. Case-Control Study • Definition • A study comparing diseased patients to non-diseased patients, looking for differences in risk factors • Use • The study of any number of risk factors or etiologies for a single disease, especially a relatively rare disease • Limitation • Certain specific biases must be avoided, e.g., historically obtained data must be complete and accurate

  17. Cohort Study • Definition • A study comparing patients with a risk factor/exposure to others without the risk factor/exposure for differences in outcome. • Use • The study of any of a number of outcomes from a single risk factor/exposure • Limitation • Prolonged and costly

  18. Case-Control Studies Disease Present(cases) Absent (controls) Present(exposed) A B Absent (not exposed) C D Factor Cohort Studies

  19. Prospective Study Retrospective Study Prospective vs. Retrospective Studies EventsUnder Study Time

  20. Experimental Study • Definition • A study in which the risk factor/exposure of interest is controlled by the investigator; randomization is generally used • Use • Most convincing demonstration of causality • Limitation • Logistic and ethical difficulties in its application to human studies

  21. Case-Control Studies Disease Present(cases) Absent (controls) Present(exposed) A B Absent (not exposed) C D Factor Cohort Studies

  22. Options in Research Design-1 • Analytic Studies • Experimental Study • Prospective Cohort Study • Retrospective Cohort Study • Case-Control Study • Descriptive Studies • Analyses of Secular Trends • Case Series • Case Reports

  23. Options in Research Design - 2 • Options in Directionality • Case-Control (case-history, case-referent, retrospective, trohoc) study • Cohort Study (follow-up, prospective) • Experimental Study (intervention trial, clinical trial) • Options in Timing • Retrospective study (retrolective, historical, non-concurrent) • Prospective study (prolective) • Cross-sectional study

  24. Options in Research Design • Experimental Study • Prospective Cohort Study • Retrospective Cohort Study • Case-Control Study • Analyses of Secular Trends • Case Series • Case Reports

  25. Sir Austin Bradford Hill “All scientific work is incomplete-- whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us a freedom to ignore the knowledge we already have, or to postpone the action that it appears to demand at a given time. “Who knows, asked Robert Browning, but the world may end tonight? True, but on available evidence most of us make ready to commute on the 8:30 the next day.” Proceedings of the Royal Society of Medicine, 1965:58;295

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