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EXPERIMENTAL EPIDEMIOLOGY
Why RCT ?
Human experiments
TYPES OF EPIDEMIOLOGICAL
STUDIES
1. OBSERVATIONAL STUDIES
A. DESCRIPTIVE STUDY
DESCRIBE DIESEASE BY
TIME
PLACE
PERSON
B. A...
Experimental studies
 In observational studies (eg. Descriptive,
case-control and cohort ) no action is
taken . The epide...
Aims of experimental studies
 To provide scientific proof of etiological (or
risk) factor which may permit modification
o...
Types of Experimental studies
 Randomized Controlled Trials
 Non- Randomized or “Non- Experiment”
trials (those departin...
Randomized Controlled Trial (RCT)
(Synonym: Randomized Clinical Trial)
”An epidemiological experiment in which subjects
in...
Design of a randomized trial
Hierarchy of Epidemiologic Study Design
Why RCT?
 GOLD STANDARD of study design
 Makes group comparable
 Controls for confounding (known and
unknown)
 Prevent...
Basic steps of RCT
1. The protocol
2. Selecting reference and
experimental populations
3. Randomization
4. Intervention
5....
Population hierarchy for intervention study
Reference population
Experimental population
Exclusion criteria
Informed conse...
1. The protocol
- Rationale
- Aims and objectives, Research questions
- Design of the study: selection of study and
contro...
2. Selecting Reference and Experimental
Populations
a. Reference or target population - population to
which the findings o...
Participants must fulfill the following criteria:
- Must give informed consent
- Should be representative of the populatio...
The critical element of randomization is the
unpredictability of the next assignment
3. Randomization
- Heart of the control trial
- Procedure: Participants are allocated
into study and control groups
- Elim...
Both groups should be alike with regards to
certain variables that might affect the
outcome of the experiment
4. Manipulation / Intervention
- Deliberate application or withdrawal or
reduction of a suspected causal factor
- It creat...
Types of Interventions
 Interventions
 Pharmaceutical (Therapeutic or Preventive)
 Device
 Procedure
 Behaviour modif...
5. Follow Up
- Implies examination of the experimental
and control group subjects
- at defined intervals of time,
- in a s...
6. Assessment
- Positive results
- Negative results
- Biases: Subject variation, Observer bias,
Evaluation bias
- Can be c...
Double-Blinded Single-Blinded
• Single
• patient doesn’t know
• Double
• neither patient nor investigator knows
• Triple
• none of the patients, investi...
Randomization is a key feature
And heart of RCT
Random = governed by chance
Randomization = allocation of individuals
to groups by chance
Each sampling unit has the same ...
Why is randomized assignment of
intervention so important?
 Randomization is so important because
overall, it provides th...
How randomization is done
 Table of Random numbers
 Computer generated list
 According to date of birth (odd or even
ye...
Ensures unpredictabilty
Simple randomisation
Stratified randomisation
Design variations
 Concurrent Parallel study designs
 Cross over designs
Randomized Controlled Trial (RCT)
Cross over
Types of RCT
 Clinical Trials- Diagnostic, Therapeutic,
Prophylactic, Devices, Procedures,
Regimens, Protocols streptomyc...
Types of Randomized Controlled Trials:
1. Clinical Trial
- Concerned with evaluating therapeutic
agent, mainly drugs
eg. E...
2. Preventive Trials:
- Trial of primary preventive measures eg.
Vaccines
- Analysis of preventive trials must result in
c...
3. Risk Factor Trials:
- Investigator intervenes to interrupt the
usual sequence in the development of
disease for those i...
4. Cessation Experiment:
- An attempt is made to evaluate the
termination of a habit which is considered
to be causally re...
5. Trials of Etiological Agents:
- To confirm or refute an etiological
hypothesis
6. Evaluation of Health Services:
- Domi...
Efficacy and effectiveness
 Efficacy – Does the intervention work in
IDEAL situations
 Effectiveness – Does the interven...
Reduction in risk or efficacy of a trial
Rate in those who Rate in those who
received placebo who received intervention
Ra...
Clinical Trial Phases
An overlapping continuum
Safety
Feasibility Efficacy Effectiveness
I
II
III
IV
Safety
Other types of evaluation designs
 Uncontrolled Trials
 Natural Experiments
 Before after study
 Non randomized trials
Conclusion
• Well-conducted double-blind randomised
controlled trials are gold standard for studies
of efficacy
•Minimise ...
Thank You …….
Questions
 Long questions
 Short notes
 Comments
 Compare
 Viva
Randomized Controlled Trial
Randomized Controlled Trial
Randomized Controlled Trial
Randomized Controlled Trial
Randomized Controlled Trial
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Randomized Controlled Trial

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Randomized Controlled Trial

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Randomized Controlled Trial

  1. 1. EXPERIMENTAL EPIDEMIOLOGY
  2. 2. Why RCT ?
  3. 3. Human experiments
  4. 4. TYPES OF EPIDEMIOLOGICAL STUDIES 1. OBSERVATIONAL STUDIES A. DESCRIPTIVE STUDY DESCRIBE DIESEASE BY TIME PLACE PERSON B. ANALYTICAL STUDIES ECOLOGICAL STUDY CROSS SECTIONAL STUDY CASE-CONTROL STUDY COHORT STUDY 2. EXPEREMENTAL STUDIES RANDOMIZED CONTROLLED TRIAL (RCT) FIELD TRIAL COMMUNITY TRIAL “RCT" by Dr Naresh 7
  5. 5. Experimental studies  In observational studies (eg. Descriptive, case-control and cohort ) no action is taken . The epidemiologist observe only the natural course of event.  The Experimental studies are similar to cohort studies except they involve some action, intervention, or manipulation
  6. 6. Aims of experimental studies  To provide scientific proof of etiological (or risk) factor which may permit modification or control  To provide the method of measuring the effectiveness and efficiency of health services for prevention, control and treatment of disease and improve the health of the community.
  7. 7. Types of Experimental studies  Randomized Controlled Trials  Non- Randomized or “Non- Experiment” trials (those departing from strict randomization for practical purposes )
  8. 8. Randomized Controlled Trial (RCT) (Synonym: Randomized Clinical Trial) ”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 intervention” John M.Last, 2001
  9. 9. Design of a randomized trial
  10. 10. Hierarchy of Epidemiologic Study Design
  11. 11. Why RCT?  GOLD STANDARD of study design  Makes group comparable  Controls for confounding (known and unknown)  Prevents selection bias
  12. 12. Basic steps of RCT 1. The protocol 2. Selecting reference and experimental populations 3. Randomization 4. Intervention 5. Follow up 6. Assessment
  13. 13. Population hierarchy for intervention study Reference population Experimental population Exclusion criteria Informed consent Excluded Refused Study population Intervention group Control group Outcome Losses to follow-up Losses to follow-up Random allocation
  14. 14. 1. The protocol - Rationale - Aims and objectives, Research questions - Design of the study: selection of study and control groups - Ethics: patient consent, adverse events - Documentation - Procedure 17
  15. 15. 2. Selecting Reference and Experimental Populations a. Reference or target population - population to which the findings of the trial, if found successful, are expected to be applicable (eg. drugs, vaccines, etc.) b. Experimental or study population - actual population that participates in the experimental study 18
  16. 16. Participants must fulfill the following criteria: - Must give informed consent - Should be representative of the population - Should be qualified or eligible for the trial 19
  17. 17. The critical element of randomization is the unpredictability of the next assignment
  18. 18. 3. Randomization - Heart of the control trial - Procedure: Participants are allocated into study and control groups - Eliminates bias and allows comparability - 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 24
  19. 19. Both groups should be alike with regards to certain variables that might affect the outcome of the experiment
  20. 20. 4. Manipulation / Intervention - Deliberate application or withdrawal or reduction of a suspected causal factor - It creates an independent variable 26
  21. 21. Types of Interventions  Interventions  Pharmaceutical (Therapeutic or Preventive)  Device  Procedure  Behaviour modification
  22. 22. 5. Follow Up - Implies examination of the experimental and control group subjects - at defined intervals of time, - in a standard manner, with equal intensity, under the same given circumstances - Attrition: Inevitable losses to follow up 28
  23. 23. 6. Assessment - Positive results - Negative results - Biases: Subject variation, Observer bias, Evaluation bias - Can be corrected by blinding 29
  24. 24. Double-Blinded Single-Blinded
  25. 25. • Single • patient doesn’t know • Double • neither patient nor investigator knows • Triple • none of the patients, investigators or analysts know Blinding/ MASKING
  26. 26. Randomization is a key feature And heart of RCT
  27. 27. Random = governed by chance Randomization = allocation of individuals to groups by chance Each sampling unit has the same chance of selection Makes intervention and control group comparable at the start of the investigation
  28. 28. Why is randomized assignment of intervention so important?  Randomization is so important because overall, it provides the strongest evidence for causal inference
  29. 29. How randomization is done  Table of Random numbers  Computer generated list  According to date of birth (odd or even years), the number of their hospital records, the date at which they are invited to participate in the study (odd or even days), or alternatively into the different study groups
  30. 30. Ensures unpredictabilty
  31. 31. Simple randomisation
  32. 32. Stratified randomisation
  33. 33. Design variations  Concurrent Parallel study designs  Cross over designs
  34. 34. Randomized Controlled Trial (RCT)
  35. 35. Cross over
  36. 36. Types of RCT  Clinical Trials- Diagnostic, Therapeutic, Prophylactic, Devices, Procedures, Regimens, Protocols streptomycin for treating TB  Preventive Trials- pertusis vaccine  Risk factor Trials- MRFIT  Cessation Experiments- eg smoking  Trial of aetiological agents- eg. Retrolental fibroplasia
  37. 37. Types of Randomized Controlled Trials: 1. Clinical Trial - Concerned with evaluating therapeutic agent, mainly drugs eg. Evaluation of beta-blockers in reducing cardiovascular mortality - Not all clinical trials are susceptible to being blinded 46
  38. 38. 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 47
  39. 39. 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 48
  40. 40. 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 49
  41. 41. 5. Trials of Etiological Agents: - To confirm or refute an etiological hypothesis 6. Evaluation of Health Services: - Domiciliary treatment of PTB was as effective as more costlier hospital or sanatorium treatment 50
  42. 42. Efficacy and effectiveness  Efficacy – Does the intervention work in IDEAL situations  Effectiveness – Does the intervention work in ‘real world’ conditions?
  43. 43. Reduction in risk or efficacy of a trial Rate in those who Rate in those who received placebo who received intervention Rate in those who received placebo
  44. 44. Clinical Trial Phases An overlapping continuum Safety Feasibility Efficacy Effectiveness I II III IV Safety
  45. 45. Other types of evaluation designs  Uncontrolled Trials  Natural Experiments  Before after study  Non randomized trials
  46. 46. Conclusion • Well-conducted double-blind randomised controlled trials are gold standard for studies of efficacy •Minimise bias •Maximise attribution
  47. 47. Thank You …….
  48. 48. Questions  Long questions  Short notes  Comments  Compare  Viva

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