Randomized control trial is so called because the patients who constitute the unit of study are allocated into ‘study group’ and ‘control group’ at random depending upon whether they receive or do not receive the intervention.
2. • Randomized control trial is so called because the patients who constitute
the unit of study are allocated into ‘study group’ and ‘control group’ at
random depending upon whether they receive or do not receive the
intervention.
• Random allocation eliminates bias.
• It is to test the efficacy of a new drug or a new drug regimen or a new
therapeutic or surgical procedure.
3. BASIC STEPS IN CONDUCTING A CLINICAL TRIAL
1. Drawing of a protocol
2. Selecting reference population
3. Randomizations
4. Manipulation
5. Follow up
6. Assessment of outcome
7. Reporting
4. DRAWING OF A PROTOCOL
This means specifying the following basic information before the
commencement of a clinical trial they are-
1. Aims and objectives of the study
2. Criteria for the selection of study group and control group
3. Size of the sample
4. Procedures for allocation into study group and control group
5. Intervention to be done
6. The co-operation of the participants till the end of the study
5. SELECTION OF REFERENCE POPULATION
• Reference population is the target population, to which the results if found
successful, are expected to be applicable.
• Reference population, depending upon the study, could be all suffering
from the particular disease under experiment.
• Example Tuberculosis, Leprosy patients for new therapy or patients with
Hernia for new surgical procedure.
6. RANDOMIZATION
• Randomization is the heart of the clinical trial.
• Every individual has an equal chance of being selected into either study
group or control group from the reference population.
7. SELECTION OF STUDY GROUP
• It is the actual population derived from the reference population, randomly
participating in the experiment, still retaining the same characteristics as the
reference population.
• Randomisation eliminates bias and allows comparability.
• The study group receives the intervention.
• The study group should fulfil the following three criteria –
1. It should be ‘Representative’ of the reference population.
2. They must give ‘informed consent’, after being fully inform about the
procedure and possible dangers of the trial.
3. They must be ‘Susceptible’ to the disease under study.
Example: suppose the trial is on the effect of a new drug of Anaemia, the
volunteers must be anaemic.
8. SELECTION OF CONTROL GROUP
Another group of the same size as that of the study group is selected at
random from the reference population, maintaining the similar characteristics
(i.e. Age, Sex, Occupation, Literacy level, Income) as that of the study group
but they do not receive intervention.
9. MANIPULATION OR INTERVENTION
The next step is to intervene or manipulate the study group by the
planned application or reduction of the casual factor, i.e. new drug, whereas
a control group is put on the inert (or placebo) the old drug.
10. FOLLOW UP
• This consists of examination of both the groups at defined intervals of time for
the time framed and the results are submitted to the statistician.
• At times some, some losses occurs to follow up due to death or migration or
non-cooperation of the participants which may affect to the results.
Therefore efforts must be made to minimise the losses during follow-up.
11. ASSESSMENT OF OUTCOME
• This is the final step of clinical trial.
• The results may be positive(e.g. the new drug is better and safer) or maybe
negative (e.g. the new drug is not good and/ or more hazardous)
• The incidence of results is compared in both the groups and the differences
are tested for the test of significance.
• Bias may arise from the three sources resulting in errors as follows-
a) Subject variation: patients may report better/improvement if they know, that
they are under new treatment.
b) Observer bias: it is made by the investigator while observing.
c) Bias in evaluation: it is made by the investigator subconsciously
12. In order to overcome this errors and bias a technique known as blinding is
adapted which is done in three ways.
1. SINGLE BLIND TRIAL
In this type the participants do not know whether they belong to study group or
control group. That means, they do not know whether they are receiving new drug or
the placebo. However, the investigator knows who belong to which group this trail
helps to overcome subject variation.
2. DOUBLE BLIND TRIAL
In this type neither the investigator, nor the participants know the group allocation
and the treatment received. However statistician knows it. He assigns the code
numbers and hand over the drugs with code number to the investigator indicating
which one to be given to whom. At the end, the results are given back to statistician
along with the code numbers for analysis. He will decode and analyse the results.
3. TRIPLE BLIND TRIAL
In this type it goes, one step further. All the participants doctors and the statisticians
are unaware of the group allocation. The findings of the trial by the doctor are handed
over to the statistician, with code numbers. He will decode and analyse the results.
Ideally double-blind trial is a most frequently used method.
14. REFERENCE
• Community Medicine with Recent advances (A H SURYAKANTHA) Chapter 18:
Principles and Practice of Epidemiology.
• Park’s textbook of Preventive and Social Medicine (K PARK) Chapter 03:
Principles of Epidemiology and Epidemiologic Methods.
