Transcript Experimental Study

EXPERIMENTAL EPIDEMIOLOGY
• INTERVENTION STUDY
• EXPERIMENTAL STUDY
• RANDOMIZED CONTROLLED
TRIALS
• In which experiment or trials are
made and results are watched.
EXPERIMENTAL STUDIES
• Experimental studies are similar in
approach to cohort studies excepting
that the conditions in which study is
carried out are under direct control of
the investigator.
EXPERIMENTAL STUDIES
• Involve some action, intervention or
manipulation:
– Application of a drug, vaccine
– Withdrawal of certain factor
– Changing one variable in exp. group
and no change in control group & then
observing &comparing the out come of
two groups
EXPERIMENTAL STUDIES
• The researcher manipulates a
situation and measures the effects of
the manipulation. Usually two groups
are compared, one in which the
intervention takes place (treatment
with a certain drug) and the other
remains untouched (treatment with a
placebo).
AIMS OF EXPERIMENTAL STUDIES
• To provide scientific proof of
aetiological factors which may permit
modifications or control of those
diseases.
• To provide a method of measuring
the effectiveness and efficiency of
health services for prevention, control
and treatment of diseases and
improve the health of the community.
ANIMAL STUDIES
• Contributed to our knowledge
• Reproduction of human diseases in
animals to confirm aetiological hypothesis,
mechanism of disease occurrence
• Testing the efficacy of preventive and
therapeutic measures e.g. vaccine, drugs
• Completing the natural history of diseases
ANIMAL STUDIES
• ADVANTAGES:
– animals can be bred in laboratories and manipulated
easily a/c to wishes of the investigator
– Animals multiply rapidly and enable the investigator to
carry out experiments
• LIMITATIONS:
– Not all human diseases can be reproduced in animals
– Conclusions derived from animal experiments may
not be applicable to human beings.
EXPERIMENTAL STUDIES
• Most incisive approach to scientific
problem, the only study that can prove
causation.
• Ethical problems, Logistic considerations
• Benefits of the study must be weighed
against risks
• Persons involved in research must be fully
informed about all possible consequences
of the experiment.
Steps in Experimental Study
• 1. Drawing up of a protocol
• 2. Selection of reference and
experimental population
• 3. Randomization
• 4. Manipulation or intervention
• 5. Follow up
• 6. Assessment of outcome
1.Drawing up of a protocol
• To specify aims and objectives of the study
• Questions to be answered
• Criteria for the selection of study and control
group
• Size of the sample
• Procedures for allocation of subjects into study
and control groups
• Action, treatment to be applied
• Schedule and evaluation of outcome of the study
• Protocol must be adhered throughout the study.
2. Selection of reference &
experimental population
• Reference or target population
– Population in which findings of trial are expected to be
applicable
• Experimental or study population
– Derived from reference population
– Randomly chosen group from reference population
– Chose a stable population
• Informed consent
• Representative of the population
• Eligible for the trial
3. RANDOMIZATION
• A statistical procedure by which participants are
allocated into groups i.e. study and control to
receive or not to receive a preventive,
therapeutic procedure or intervention.
• Each subject is given an equal
opportunity/chance of being assigned to either
group and blindly selecting the numbers for each
group.
• Randomization allows comparability and
eliminates errors.
Manipulation
• Intervene or manipulate the study group
– Application of
– Withdrawal of
– Reduction of suspected causal factor
• Independent variable whose effect is
determined by measurement of final
outcome that constitutes the dependent
variable.
Follow up
• Examination of control and study groups at
regular intervals
– Standard manner
– Equal intensity
– Same conditions
• Duration must be sufficient to demonstrate
a significant difference
• Follow up may be short or long
• Minimize the losses to follow up.
Assessment
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Positive results
Negative results
Comparison of results in both groups
Differences are tested statistically
ERRORS
– Subject variation
– Observer variation
– Bias in evaluation
BLINDING
• The concealment of group assignment
from the knowledge of the patients and/ or
investigators in a clinical trial.
• Blinding eliminates possibility
– The knowledge of assignment may
affect patient response to treatment
– The Investigator’s behaviour that may
affect outcome
SINGLE BLIND TRIAL
• The participant is not aware
whether he belongs to a study or
control group
• Knowledge of group assignment
is with held only from patients.
DOUBLE BLIND TRIAL
• The trial is so planned that neither
the doctor nor the participant is
aware of the group allocation and
treatment received
• Knowledge of group assignment
is with held from patients and
investigators
TRIPLE BLIND TRIAL
• The participant, the Investigator and
the person analyzing data are all
blind.
• Knowledge of assignment is with held
from patients, investigators and
analyst.
Experimental study
Quasi-experimental study design
Study Group
Before
Intervention
study group
after
Compare
Control group
Before
control group
after
SELECTION OF STUDY DESIGN
• Type of information you want to obtain
• Devise strategies to enable to obtain that
information.
• The selection of an appropriate study design
depends on:
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The state of knowledge about the problem
The nature of the problem and its environment.
The resources available for the research
Objectives of the study.
CASE
• A person who has a particular
disease, health disorder or
condition which meets a set of
diagnostic criteria to be regarded
as a case of disease and for
surveillance and outbreak
investigation purpose.