Clinical trials are research studies that aim to evaluate the safety and efficacy of new medical interventions, such as drugs, devices, or treatments. To conduct a clinical trial, researchers need to carefully design the study in order to answer specific research questions and obtain reliable and valid results. There are several types of study designs that can be used in clinical trials, each with its own strengths and limitations. Some common study designs include: Randomized controlled trials (RCTs): In an RCT, participants are randomly assigned to either an intervention group or a control group. The intervention group receives the treatment or intervention being studied, while the control group may receive a placebo or standard of care. RCTs are considered the gold standard for clinical trials because they minimize bias and provide strong evidence of causality. Observational studies: Observational studies are non-randomized studies that observe and analyze participants over time to identify potential associations between risk factors and outcomes. These studies are often used when it is not ethical or feasible to conduct an RCT. Cross-sectional studies: In a cross-sectional study, researchers collect data from a sample of participants at a single point in time. This type of study is often used to describe the prevalence of a disease or condition within a population. Cohort studies: In a cohort study, researchers follow a group of participants over time to identify potential risk factors and outcomes. Cohort studies can be either prospective (the researchers follow the participants from the present into the future) or retrospective (the researchers analyze data from past events). Overall, the choice of study design depends on the research question, the characteristics of the population being studied, and the resources available for the study. By carefully selecting and implementing the appropriate study design, researchers can gather reliable and valid data to inform clinical practice and improve patient outcomes.

1. Welcome
Study designs in Clinical Trial
Name : Talari Neharika
Qualification : Pharm. D
Student ID : 006/012023
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2. INTRODUCTION:
Research study design is the formulation of trials and experiments, and observational studies in medical,
clinical and other types of research involving human beings. The aim of clinical study is to assess safety,
efficacy and mechanism of investigational medical product or procedure, or new drug or device that is in
development.
Types of Study designs in Clinical Trial:
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Non randomized control studies
Descriptive
Randomized controlled trials
Observational studies
Interventional / Experimental studies
Study designs
Analytical
Blinded studies
Non blind / un blind / open studies Case report
Case control
Cross sectional
Case series
Surveys
Cohort
Adaptive studies

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An epidemiological experiment in which subjects are randomly allocated into groups, usually called
study and control. Gold standard study. Subjects are randomly assigned in order to avoid bias.
It is a comparative study with statistical reliability.
(a) Simple:
Single sequence of random assignments is simple randomization. The most common and basic
method of simple randomization is flipping a coin. Two treatment groups (control versus treatment) are
side of the coin i.e., heads - control, tails – treatment.
(b) Stratified:
Stratified randomization is grouping of subjects by using age group or gender or race.
1. Interventional/Experimental studies:
Patients are selected on basis of selection criteria. They are not randomized to particular treatment and
are given a treatment depending upon course of disease.
(1) Randomized Control Trial:

4. Strata
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Eligible
subjects
1
3
2
Patient Treatment
1 A
2 A
3 B
4 B
5 B
6 A
7 B
8 B
9 A
10 A
Allocation Final Group
I
C
(a) Simple randomization
(b) Stratified randomization
Blinding assist in bias elimination in study participants, follow up examiners, treatment administrators,
staff involved in the study. It can be prevented at different levels by hiding or blinding or masking.
Blinding is three types based upon the persons blinding in the study.
Single blinding ( patient kept unaware)
Double blinding (patient and clinician are kept unaware)
Triple blinding (patient, clinician and statistician are kept unaware)
(2) Blinded studies:
Single Double Triple
Subject x x x
Clinician x x
statistician x

5. Parallel study:
The parallel study is a simplest and widely used study. In this study interventional group
receive interventional drug and control group receive old drug or Placebo throughout the
study.
Cross over study:
In cross-over study both groups receive both drugs. Interventional group receive
interventional drug and control group receive old drug or placebo, after the washout period
the treatments are exchanged then interventional group receive old drug or placebo and
control group receive interventional drug.
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Basic types of Randomized Control Study Design:
(3) Non-blind / Un-blind / Open studies:
In this researchers know what treatments are being given to each study subject or experimental
group. If human subjects are involved , they know what treatments they are receiving.
A
B
A
B
A
B A
B
(a) Parallel study (b) Cross over study
Washout period
A – Placebo / Reference drug
B – Active drug

6. Single / Multi centered:
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By implementing Adaptive Trial Designs you have the opportunity to carefully evaluate clinical data in
real-time, so you can make informed decisions to change the direction of study for a better chance of
success. A well-designed and executed Adaptive Trial Design can:
(a) Increase the probability of success for your new therapy
(b) Maximize the information from the trial
(c) Shorten development timelines
(d) Reduce overall development costs
(e) Reduce the risk for study volunteers and sponsors
(f) Maximize the probability of success with regulators and payers
(4) Adaptive studies:
(5) Non Randomized control trial:
The study is same as that of the randomized control study but without randomization. The control group
receive placebo or old drug and interventional group receive interventional drug finally outcomes are
measured.
Hospital Investigator Sponsor Protocol
Single center 1 1 1 Same
Multi center >1 >1 1 Same

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2. Observational:
In this the subjects or recruited population are just observed, no interventions are taken place. Main goal of the
various study designs include Descriptive study to generate hypothesis, Analytical study is to test hypothesis and
Experimental study is to prove hypothesis.
Cohort study is a prospective study. The study consists two group’s first group is exposed to some risk
factor and second group free from exposure. Compare the disease risk between exposed group and
unexposed group. Cohort study measures,
Incidence = Number of new cases during specified period
Total persons was observed in specified period
(a) Cohort study:
(1) Analytical study:
Relative risk = Outcome of exposed to a drug
Outcome of unexposed group
to a drug

8. Risk difference = outcome of exposed group – outcome of non-exposed group
Case-control study the study start with outcome and search for the risk factor by taking case records.
This study includes case group (people with diseases) and control group (people without disease) as a
comparison. is a retrospective study that means opposite to cohort study.
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(b) Case control study:
Measures exposure and outcome at the same time in randomly selected population. Conducted
through surveys, database analysis or medication chart reviews. Data available readily, good for
assessing the prevalence.
(C) Cross sectional study:
Point prevalence = Cases during a given specified point of time
total population during the period
× 100
Period prevalence = Cases during a given time period
total population during the same
time period
× 100

9. (2) Descriptive studies:
Case reports are useful to set hypothesis for causation of an event. So it gives alarming signal for
other health care professionals on the event. But case report should be details of a rare disease,
abnormal drug reaction and ADRs. This rare events are have been collected by the WHO, Uppsala
monitoring center.
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(a) Case reports:
(b) Case series:
Example: Case report on Thalidomide that causes human Teratogenicity, later helped to confirm
that could produce fetal abnormalities.
Case series are collection of case reports, who have a similar single exposure or similar outcomes.
Case series are mainly useful to find out the ADRS. It is also named as open trail.
The collection of information from a group. The types of information include – Demographics,
Attitudes, Opinions, Knowledge and Behaviors. There are several steps involved in conduct the
survey as follows:
(c) Survey:
Frame the research question
Develop the survey
Pilot text of the survey

10. Bias:
Bias or errors in the study causes the results inaccurate. The different biases include,
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1. Selection Bias:
Selection bias is a problem in observational studies, because groups are not randomization. Groups
assigned as their wish. If groups are not balanced based on the characteristics, we get irregular and
unbalanced groups, ultimately it effects on results.
2. Information Bias
The inaccurate information collected from subjects, results in giving the wrong outcome. This inaccurate
information may come from the either subjects or personnel.
3. Measurement Bias
If many groups are involved in the study, the personnel measuring, instruments used are the two major
problems to arise this bias.
4. Protopathic Bias
The electing of a diseased person but not recognized during commencing the study, disease may appear
after the drug intake cause to misleading of the study.

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