Experimental study design.pptx

this ppt contains basics of experimental design concepts for 2nd year mbbs students, and third year mbbs students,

1. Experimental Study Designs

2. SGD-5,CM7.5 Describe & Discuss Experimental Study Designs Date-06/04/2023 Group 1 4/6/2023 9:37 AM Dr Chirag R. Sonkusare 2

3. Epidemiology The study of the occurrence and distribution of health-related events, states, and processes in specified populations, including the study of the determinants influencing such processes and the application of this knowledge to control relevant health problems." 06/04/2023 09:30 Dr Chirag R. Sonkusare 3

4. Classification of Epidemiological studies 4/6/2023 9:30 AM Dr Chirag R. Sonkusare 4

5. Experimental study design 06/04/2023 09:30 Dr Chirag R. Sonkusare 5 Aims of experimental studies To provide ''scientific proof" of aetiological (or risk) factors that 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 health of the community.

6. Experimental study design 06/04/2023 09:30 Dr Chirag R. Sonkusare 6 Animal Experiments: Experiments Webster in United States Topley, Wilson and Greenwood in England Classical animal experiments. Their studies centred round inducing epidemics in animals and in studies of herd immunity under laboratory conditions

7. Experimental study design 06/04/2023 09:30 Dr Chirag R. Sonkusare 7 Human Experiments Human Experiments James Lind Human experiment in which he added different substances to diet of 12 soldiers who were suffering from scurvy. Edward Jenner Experiment with Cowpox Finlay and Reed Experiment to elucidate the mosquito borne nature of yellow fever. Goldberger Experiment inducing pellagra by diets deficient in nicotinic acid.

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9. Introduction: RCT is an epidemiologic experiment. oral hypoglycaemic agents, varicose veins stripping, tonsillectomy, hospitalisation of all patients with myocardial infarction, multiphasic screening and applicability of many preventive and therapeutic procedures . 06/04/2023 09:30 Dr Chirag R. Sonkusare 9 Randomized controlled trials (RCT)

10. Basic steps in conducting RCT: Drawing up a protocol Selecting reference and experimental population Randomization Manipulation or intervention Follow-up Assessment of outcome. 06/04/2023 09:30 Dr Chirag R. Sonkusare 10 Randomized controlled trials (RCT)

11. Design of Randomized Control Trial : 06/04/2023 09:30 Dr Chirag R. Sonkusare 11 Select suitable population (Reference or Target population) Select suitable sample (Experimental or study population) Make necessary exclusions Those not eligible Those who do not wish to give consent RANDOMIZE Experimental group Control group Manipulation and follow-up ASSESSMENT Randomized controlled trials (RCT)

12. 1. Drawing up a protocol: The protocol specifies the Aims and objectives of the study, Questions to be answered, Criteria for the selection of study and control groups, Size of the sample, The procedures for allocation of subjects into study and control groups, treatments to be applied- When and where, and how to what kind of patients, Standardization of working procedures and Schedules as well as responsibilities of the parties involved in the trial, up to the stage of evaluation of the outcome of the centres participating in the trial. The protocol aims to prevent bias and reduce the study's sources of error . 06/04/2023 09:30 Dr Chirag R. Sonkusare 12 Randomized controlled trials (RCT)

13. 2. Selecting reference and experimental populations: Reference or Target population : It is the population to which the findings of the trial if found successful, are expected to be applicable (e.g., a drug, vaccine or other procedures). Experimental or study population: It is derived from the reference population. It is the actual population that participates in the experimental study. The participants or volunteers must fulfil the following criteria: - They must give informed consent. - They should be representative of the population to which they belong. - They should be qualified or eligible for the trial. 06/04/2023 09:30 Dr Chirag R. Sonkusare 13 Randomized controlled trials (RCT)

14. 3. Randomization: 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 experimental preventive or therapeutic procedures , manoeuvres or interventions. Randomization is an attempt to eliminate bias and allow for comparability. Randomization is the heart of a clinical trial. 06/04/2023 09:30 Dr Chirag R. Sonkusare 14 Randomized controlled trials (RCT)

15. 4. Manipulation: Intervene or manipulate the study (experimental) group by applying, withdrawing, or reducing the suspected causal factors. Manipulation creates an independent variable (e.g., drug, vaccine, a new procedure) whose effect is then determined by measurement of the final outcome, which constitutes the dependent variable (e.g., the incidence of disease, survival time). 06/04/2023 09:30 Dr Chirag R. Sonkusare 15 Randomized controlled trials (RCT)

16. 5. Follow-up: This implies the examination of experimental and control group subjects at defined intervals of time, in a standard manner, with equal intensity, under the same given circumstances, in the same time frame till the final assessment of the outcome. The follow-up may be short or require many years, depending on the study undertaken. 06/04/2023 09:30 Dr Chirag R. Sonkusare 16 Randomized controlled trials (RCT)

17. 6. Assessment: The final step is an assessment of the outcome of the trial in terms of : Positive results: Benefits of the experimental measures such as reduced incidence or severity of the disease, the cost to the health service or other appropriate outcomes in the study and control groups. Negative results: severity and frequency of side effects and complications. Bias may arise from errors of assessment of the outcome due to human element. May be from the three sources: - Bias on the part of the participant - Observer bias - Bias in evaluation 06/04/2023 09:30 Dr Chirag R. Sonkusare 17 Randomized controlled trials (RCT)

18. Blinding: Blinding can be done in three ways: Single Blind Trial: The participant is unaware whether he belongs to the study or the control group. Double Blind Trial: Neither the doctor nor the participant knows the group allocation. Triple Blind Trial: The participant, the investigator, and the person analysing the data are all blind. 06/04/2023 09:30 Dr Chirag R. Sonkusare 18 Randomized controlled trials (RCT)

19. Types of RCT: 1. Clinical trials 2. Preventive trials 3. Risk factor trials 4. Cessation experiments 5. Trial of etiological agents 6. Evaluation of health services 06/04/2023 09:30 Dr Chirag R. Sonkusare 19 Randomized controlled trials (RCT)

20. 1. Clinical trials: For the most part, clinical trials have been concerned with evaluating therapeutic agents, mainly drugs. - Evaluation of beta blockers in reducing cardiovascular mortality in patients surviving the acute phase of myocardial infarction. - Trials of folate treatment/ supplementation before conception - Trials of aspirin on cardiovascular mortality - Efficacy of tonsillectomy for recurrent throat infection. Unfortunately, not all clinical trials are susceptible to being blinded. Many ethical, administrative and technical problems are involved in the conduct of clinical trials. 06/04/2023 09:30 Dr Chirag R. Sonkusare 20 Randomized controlled trials (RCT)

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23. 2. Preventive trials (Field trial): Preventive trials are purported to prevent or eliminate disease on an experimental basis. The most frequently occurring type of preventive trials are the trials of vaccines and chemoprophylactic drugs. Analysis of a preventive trial must result in a clear statement. A) The benefit the community will derive from the measure B) The risks involved C) The costs to the health service in terms of money, men and material resources. 06/04/2023 09:30 Dr Chirag R. Sonkusare 23 Randomized controlled trials (RCT)

24. 3. Risk factor trials: A type of preventive trial is the trial of risk factors in which the investigator intervenes to interrupt the usual sequence in the development of disease for individuals with “risk factors” for developing the disease. Risk factor trials can be a single factor or multi-factor. Example: The major risk factors for coronary heart disease are elevated blood cholesterol, smoking, hypertension, and sedentary habits. Main possibilities of intervention in coronary heart disease are the reduction of blood cholesterol, the cessation of smoking, the control of hypertension, and the promotion of the regular physical activity. 06/04/2023 09:30 Dr Chirag R. Sonkusare 24 Randomized controlled trials (RCT)

25. 4. Cessation experiments: Another type of preventive trial. An attempt is made to evaluate the termination of a habit which is considered to be causally related to a disease. The example is cigarette smoking and lung cancer. 06/04/2023 09:30 Dr Chirag R. Sonkusare 25 Randomized controlled trials (RCT)

26. 5. Trial of aetiological agents: One of the aims of experimental epidemiology is to confirm or refute an aetiological hypothesis. The best-known example trial of an aetiological agent relates to retrolental fibroplasia. 06/04/2023 09:30 Dr Chirag R. Sonkusare 26 Randomized controlled trials (RCT)

27. 6. Evaluation of health services: Randomized control trials have been extended to assess the effectiveness and efficiency of health services. The necessity of choice arises from the fact that resources are limited, and priorities must be set for the implementation of a large number of activities that could contribute to the welfare of society. An excellent example of such an evaluation is the controlled trials in the chemotherapy of Tuberculosis in India. 06/04/2023 09:30 Dr Chirag R. Sonkusare 27 Randomized controlled trials (RCT)

28. Introduction: Approach is sophisticated in randomised control trials but rather crude in non-randomized trials. As there is no randomisation in non-experimental trials, the degree of comparability will be low and the chances of a spurious result higher than where randomisation had taken place. 06/04/2023 09:30 Dr Chirag R. Sonkusare 28 Non-randomized / Non-experimental trials

29. Examples- Uncontrolled Trial: There is room for uncontrolled trials (i.e., trials with no comparison group) Example- There were no randomised controlled studies of the benefits of the pap test when it was introduced. Today, there is indirect epidemiological evidence from well over a dozen uncontrolled cervical cancer screening studies that the pap test effectively reduces mortality from the disease. 06/04/2023 09:30 Dr Chirag R. Sonkusare 29 Non-randomized / Non-experimental trials

30. 2. Natural Experiments: Where experimental studies are not possible in human populations, the epidemiologist seeks to identify “natural circumstances” that mimic an experiment. Example- In respect of cigarette smoking, people have separated themselves “naturally” into two groups, smokers and non-smokers. Epidemiologist tested hypotheses regarding lung cancer and cigarette smoking. John Snow’s discovery that cholera is a water-borne disease was the outcome of a natural experiment. 06/04/2023 09:30 Dr Chirag R. Sonkusare 30 Non-randomized / Non-experimental trials

31. 3 . Before and After comparison studies: These are community trials that fall into distinct groups: a) Before and after comparison studies without control. b) Before and after comparison studies with control. 06/04/2023 09:30 Dr Chirag R. Sonkusare 31 Non-randomized / Non-experimental trials

32. Exercise- The TB chemotherapy centre wants to determine the relative risk for contact with patients treated at home and sanatorium. A controlled comparison of home and sanatorium treatment of TB for one year and subsequently for another four years to study the emergence of relapse cases in these two groups. If you are the immunisation officer of your district and want to check the efficacy of the measles vaccine, how will you proceed? 06/04/2023 12:50 Dr Chirag R. Sonkusare 32 Randomized controlled trial Randomized controlled trial Field trial

33. Thank you….. Keep Doing Experiments…. 33 4/6/2023 9:39 AM Dr Chirag R. Sonkusare