Experimental epidemiology

Epidemiology-6

1. Experimental Epidemiology BY: JAGAN KUMAR OJHA MSc. Tutor, SNC, Bhubaneswar

2. Experimental Studies Experimental studies  are ones where researchers introduce an intervention and study the effects under the direct control of the investigator” The study in which an investigator manipulates or controls one or more independent variables and observes the effect on dependent variables.

3. Unique Features of Experiment Experiments provide strongest evidence about the existence of a cause-effect relationship.

4. Aims of Experimental Epidemiology ❏ To provide “ Scientific proof ” of etiological or risk factors which may permit the modification or control of those diseases. ❏ To provide a method of measuring  the effectiveness and efficiency of health services  for the prevention, control and treatment of disease and improve the heath of the community.

5. Randomized Controlled Trials

6. ”An epidemiological experiment in which subjects in a population are randomly allocated into groups, usually called study and control groups to receive and not receive an experimental preventive or therapetuic procedure, maneuver, or interventition” John M.Last, 2001 Randomized Controlled Trials

7. ”Gold standard” in epidemiological research Makes study groups comparable Prevents selection bias Randomized Controlled Trials

8. Randomized Controlled Trial Design

9. Steps Involved In Randomized Controlled Trials Are As Follows : Drawing up a protocol Selecting reference and experimental populations( Study Population) Randomization Intervention or Manipulation Follow up Assessment of outcome

10. Drawing up a protocol Drawing up a Protocol specifies : Aims and objectives of study Questions to be answered Criteria for selection of study and control groups Size of the sample

11. Procedures for allocation of subjects into study and control groups Treatment to be applied-when ,where & how Schedules as well as responsibilities of parties involved in the trial up to the outcome of the study Drawing up a protocol…

12. Selecting reference and experimental populations The experimental population is selected from the reference population. The results of experimental population if found successful, it is applied for the reference population .

13. Experimental population The actual group in which the trial is conducted Representive of the reference population Possibility for accurate follow up of information during the trial( stable group )

14. Reference & Study Population Reference Population Study Population

15. Selection of study population Participants must be fully informed - Purpose - Procedure Risks Benefits Willing to participate Informed consent Screened for eligibility Inclusion criteria Exclusion criteria

16. Randomization is a statistical procedure by which the participants are allocated into groups usually called “Study” and “Control” groups, to receive or not to receive an experimental, preventive or therapeutic procedure or intervention. Radomization

17. Random = governed by chance Randomization = allocation of individuals to groups by chance Each sampling unit has the same chance of selection Radomization

18. Randomization Heart of the control trial Procedure: Participants are allocated into study and control groups Both groups should be alike with regards to certain variables that might affect the outcome of the experiment - Best done by using table of random numbers

19. Ensure comparability Avoid selection bias Why randomization is important?

20. Intervene or manipulate the study group: Experimental group Application, withdrawal or reduction of suspected causal factor e.g. drug, vaccine, habit Control group no intervention, usual care, placebo Intervention

21. Examination of experimental and control groups at defined interval of time, in a standard manner, with equal intensity, in the same time frame until the final assesment of OUT COME Follow-up

22. Some losses to follow up are inevitable such as death, migration, loss of interest- " Attrition " Possible reasons for non-adherence Developing side effects Forgetting to take medication Withdrawing consent Decide alternative treatment Health issues: treatment contraindicated Extent of non-adherence is related to length of study time Attrition:

23. This is the final step of the trial. The outcome may be positive or negative. During the assessment of the outcome, bias is inevitable.  Positive (Benifits) and Negative (side effects etc..) results are compared in both groups. If there is difference, Test of Significance is applied to find out the significance. Assessment BIAS ARISE FROM ERRORS OF ASSESMENT OF THE OUTCOME

24. Study Designs Parallel study design Cross- over type of study design

25. Parallel Study Design

26. Parallel Study Design

27. Cross-Over Study Design

28. Cross-Over Study Design

29. Types of Randomized controlled trials Clinical trials Preventive trials Risk factor trials Cessation experiments Trial of etiological agents Evaluation of health services

30. Clinical Trial Concerned with evaluating therapeutic agent, mainly drugs eg . Evaluation of beta-blockers in reducing cardiovascular mortality

31. 2. Preventive Trials: Trial of primary preventive measures eg . Vaccines - Analysis of preventive trials must result in clear statement about benefits to community, risk involved and cost to health

32. 3. Risk Factor Trials: Investigator intervenes to interrupt the usual sequence in the development of disease for those individuals who have risk factor for developing the disease Primary prevention of CHD using clofibrate to lower serum cholesterol

33. 4. Cessation Experiment: An attempt is made to evaluate the termination of a habit which is considered to be causally related to disease Cigarette smoking and lung cancer

34. 5. Trials of Etiological Agents: To confirm or refute an etiological hypothesis 6. Evaluation of Health Services: To evaluate effectiveness and efficiency of health services Domiciliary treatment of Pulmonary Tuberculosis was as effective as the more costlier hospital or sanatorium treatment

35. Ethical issues Feasibility Problems of finding sufficiently large eligible sample size Costs Expensive Unique problemes of intervetion studies

36. APPLICATION OF EPIDEMIOLOGY To describe the spectrum of disease. To describe the natural history of disease. To formulate Community Diagnosis To Describe the clinical picture of a disease To Identify the factors that increase or decrease of disease To Identify precursor of disease & syndrome Test the efficacy of intervention strategies Investigation the epidemic of unknown disease Evaluate public health programme Elucidate the mechanism of disease transmission

37. ANY DOUBT?

38. SUMMARY

39. T H A N K Y O U