RANDOMIZED CONTROL trials an assessment method questions validity and applicability of many preventive and therapeutic procedures reference Park's Preventive and social medicine

1. Siwani Teki

2. Epidemiological studies
Non experimental / observational
studies
Experimental / interventional
studies
Randomized
control trials
Non
randomized
control trials

3.  It is an assessment method
 It questions validity and applicability of many
preventive and therapeutic procedures.
 Basic steps in conducting RCT :
1. Drawing up a protocol
2. Selecting reference and experimental populations
3. Randomization
4. Manipulation
5. Follow -up
6. Assessment of outcome

4. Protocol
It specifies :
 Aims and objectives of the study
 Questions to be answered
 Criteria for selection of the study and control group
 Size of sample
 Procedures for allocation of the subjects
 Treatments applied
 Standardisation of working procedures and
schedules
Aims at preventing bias and to reduce the sources of error
in study
Sometimes preliminary tests are made before the trial
begins to check the feasibility and acceptability of certain

5. Reference population:
it is the population in which the findings of the trial are
found, are expected to be applicable .
Experimental population :
• It is derived from the reference population .
• They are the potential participants .
• The participants should fulfil the following criteria:
 Must give informed consent
 Should be a representative
 Should be eligible for the trial.
It is important to take the participants from a stable
Selection of reference and experimental
population

6. • Randomization is the "heart" of a control trial.
• It is a statistical procedure by which the
participants are allocated into groups.
• It is an attempt to eliminate "bias" and allow for
comparability
• It is crucial that both the groups should be
alike with regard to certain variables or
characteristics that might affect the outcome of
the experiment.
Randomization

7. • Bias may arise from errors of assessment of the
outcome
• These may be from three sources
 Subject variation
 Observer bias
 Bias in evaluation
• In order to reduce these problems, a technique
known as "blinding" is adopted
 Single blind trial
 Double blind trial
 Triple blind trial
When an outcome such as death is being measured,
blinding is not so essential.

8. • Intervention the study group by the deliberate
application or withdrawal or reduction of the
suspected causal factor as laid down in the protocol.
• This 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.,
incidence of disease, survival time, recovery period)
Manipulation

9. • This 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, in the same time frame till final
assessment of outcome.
• It may be some losses to follow-up are inevitable due to
factors, such as death, migration and loss of interest. This
is known as ATTRITION.
• If the attrition is substantial, it may be difficult to
generalise the results of the study to the reference
population.
Follow –up:

10. (a) Positive results : benefits of the experimental measure
such as reduced incidence or severity of the disease or
other appropriate outcome in the study and control
groups.
(b)Negative results : severity and frequency of side-effects
and complications, if any, including death.
• The incidence of positive/negative results is compared in
both the groups, and if any the differences found, are
tested for statistical significance.
• Techniques are available for the analysis of data as they
are collected, but it is more useful to analyse the results
at the end of the trial.
Assessment

11. Protocol
design
Selection of population
for study
Non participantsParticipants
Potential
participants
Randomization
Study group
Control
group
Non participants
Manipulation and Follow up
Assessment
Design
Of
Randomised
Control trial

12.  Concurrent parallel study designs
comparisons are made between
two randomly assigned groups.
STUDY DESIGNS

13.  Cross-over type of study designs
• The study group receives the treatment
• The control group receives some alternate form of active
treatment or placebo .
• Then, after this period of medication the two groups are
switched.
outcom
e
outcome

14. TYPES
OF
RANDOMIZED
CONTROLLED TRIALS

15. 1.Clinical trials
• "clinical trials" have been concerned with evaluating
therapeutic agents, mainly drugs.
Not all clinical trials are susceptible to being blinded.
For example, there is no way to perform a clinical trial of
tonsillectomy without being obvious who received
surgery and reason why the value of these procedures
continues to be uncertain.
Many ethical, administrative and technical problems are
involved in the conduct of clinical trials.

16. 2. Preventive trials
• It is synonymous with primary preventive measures.
• The most frequently occurring type of preventive trials
are the trials of vaccines and chemo prophylactic drugs.
Since preventive trials involve larger number of subjects
and sometimes a longer time span to obtain results, there
may be greater number of practical problems in their
organisation and execution.

17. 3. Risk factor trials
• A preventive trial for risk factor modification in which
the investigator intervenes to interrupt the development
of disease for those individuals who have "risk factor" for
developing the disease.
• Risk factor trials can be "single-factor" or "multi-factor"
trials.

18. 4. Cessation experiments
• Another type of preventive trial.
• In this type of study, an attempt is made to evaluate
the termination of a habit which is a causative factor
of the disease.
• Example is cigarette smoking and lung cancer, and
group that has given up smoking, demonstrated
decrease in the incidence of lung cancer.

19. 5. Trial of aetiological agents :
• One of the aims of the studies is to confirm an aetiological
hypothesis.
• Since most diseases are fatal, disabling or unpleasant,
human experiments to confirm an aetiological hypothesis
is rarely possible.

20. 6. Evaluation of health services
• Randomized controlled trials have been extended to
assess the effectiveness and efficiency of health
services.
• Example of such an evaluation is the controlled trials
in the chemotherapy of tuberculosis in India, which
demonstrated that "domiciliary treatment" for
pulmonary tuberculosis was as effective as the more
costlier "hospital or sanatorium" treatment.
• These studies are also labelled as "health services
research" studies.

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