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Terminologies of Clinical trial terms

Adverse Event

“A undesirable change or medical occurrence that occurs during a clinical trial or within a certain time period after the trial has ended. An adverse event may or may not be caused by the treatment being studied.

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Arm assignment

The assignment of a group or subgroup of the participants in a clinical trial in order to receive interventions, or no interventions, as specified in the study protocol.


A procedure (eg. a blood test, scan, etc.) used to create data required by the trial.”

Background therapy

The current medicine that is regularly taken as a standard of treatment for a serious condition/disease is background therapy.


A type of clinical trial design that does not know which treatments have been allocated to which patients by one or more parties involved in the trial, such as the study team or participant.


The control or “standard care shall be measured against the treatment under investigation. It has to be proven that an accepted medication works and that the investigational treatment is compared against it in the study.

Clinical study

A research study to answer specific health issues in human volunteers.

Interventional trials determine if in controlled settings, experimental methods or innovative ways of using known therapies are safe and efficient.

Cross-over trial    

A clinical trial where two or more procedures are performed in a particular order by groups of volunteers.

For example, a “two-by-two” cross-over trial design is where at the beginning of the trial, one group receives drug A and then receives drug B for the remainder of the trial.

Participants obtain drug B first in the second category and then drug A. Thus the word “cross-over” is used to describe the order in which they are assigned, such as drug A and then drug B, or drug B and then drug A.

All participants receive both drugs during the study.

Dosing discontinuation

Point/time when for some reason, a patient volunteer permanently stops taking study medication. This could be at the end of the research or before the end if for whatever reason, the patient wishes to avoid taking the drug.


Only the study pharmacist knows what study drug a participant is taking in a double-blind experiment; the researchers, clinicians, nurses, and other clinical trial personnel are not told.

Early patient withdrawal (premature withdrawal) 

Point/time when a patient leaves a trial prior to the scheduled completion of all investigation/trial drug administration and all assessments (including follow-up).

Eligibility Criteria

The requirements that must be met for individuals who wish to engage in a clinical trial. Eligibility Requirements include, and are specified in the protocol, both inclusion criteria and exclusion criteria.


European Medicines Agency. An agency of the European Union that oversees use of the medicinal products. 


The point, or time, after informed consent was obtained, of a volunteer’s entry into the trial. For defining the number of participants in a clinical trial, the same term may also be used.


The planned stage of the volunteers’ participation in the trial.

Typical epochs are: determination of the subject eligibility, wash-out of prior treatments (i.e., a period of time when previous treatments are stopped), exposure of subject to treatment, or the follow-up on the subjects after treatment has ended.

Health Authority

A national or international health agency that has authority over and regulates a clinical study.


A disorder, symptom, or specific collection of circumstances that make a particular test, medication, treatment, or surgery advisable.

For medication, the indication refers to the use of the treatment in the treatment of a particular disease.

Informed consent

“Informed consent is the process in which a health care provider educates a patient about the risks, benefits, and alternatives of the given procedure or intervention. The informed consent form must be in patients native language or can be explained for easy understanding.

In general Informed consent requires the patient or responsible party to sign a declaration confirming that they understand the risks and benefits of the procedure or treatment.

The informed consent process means that when you know what to do, the health care provider has sent you specifics about the illness, along with monitoring and recovery choices.


Institutional Review Board (IRB)

“The Institutional Review Board (IRB) also known as an Independent Ethics Committee (IEC), Ethical Review Board (ERB), or Research Ethics Board (REB), is a kind of committee that applies research ethics by evaluating the methods used for research to ensure that they are ethical.

These boards are formally designated for the acceptance (or rejection), monitoring and review of human biomedical and behavioral studies.

The goal of the IRB is to ensure that adequate measures are taken to protect the rights and welfare of the participating human beings as subjects in a research study.

Most developing countries, along with developed countries, have established national, regional, or local IRBs to safeguard ethical conduct of research on national and international norms, laws, or codes.

The IRB is concerned with safeguarding human subjects’ health, freedoms and privacy.

The IRB has the authority to approve, oppose, track and mandate changes in all research activities falling under its jurisdiction as defined by both the federal regulations and institutional policies.


Interventional study 

Interventional clinical study is performed with the purpose of studying or representing clinical or pharmacological properties of drugs/devices, their side effects and to establish their efficacy or safety.

They also include studies in which surgical, physical or psychotherapeutic procedures are inspected.

Interventional studies are often prospective and are specially tailored to evaluate direct impacts of treatment or defensive measures on disease.

Each study design has precise outcome measures that rely on the type and quality of the data utilized.

Moreover, each study design has potential limitations that are more severe and need to be addressed in the design phase of the study.


Investigational drug 

The drug being evaluated in the trial; this definition is synonymous with “investigational new drug” or “investigational medicinal product.”

Medication number 

A specific number on the label of each investigational drug kit that is used for dispensing and monitoring drugs in the trial.

The number is used to ensure that the drug is administered in the correct amount to various test centers.

Observational study

Observational Clinical study involves giving the participant a particular treatment in accordance with clinical practice.

Observational studies are typically categorized into various categories such as case report or case series, ecologic, cross-sectional (prevalence study), case-control and cohort studies.

Other variants of these observational studies are also possible such as nested case-control study, case-cohort study etc.


Outcome measure
“In clinical trials, an event or outcome that can be measured objectively to determine whether the intervention being studied is beneficial.
The outcome measures of a clinical trial are usually included in the study objectives. Some examples of endpoints are survival, improvements in quality of life, relief of symptoms, and disappearance of the tumor.”


“A placebo is anything that seems to be a “real” medical treatment — but it doesn’t. It might be a pill, a shot, or some other type of “fake” treatment. All placebos have one thing in common is that they do not contain an active substance meant to affect health.

Normally, the person getting a placebo doesn’t know for sure that the treatment isn’t real.

The placebo is often in the form of a “sugar pill,” but it may also be an injection, a liquid, or even a procedure. This is intended to act like a true cure, but it does not affect the disease directly.

Principal Investigator

The individual responsible for the scientific and technological direction of the clinical trial at a specific clinical site. In most cases, the principal investigator would be a leading physician in the disease field being investigated.


“A protocol for clinical trials is a document outlining how a clinical trial should be performed, including the objective(s), design, methodology, statistical considerations and structure of the study to ensure participants’ health and the validity of the data collected.


Randomized allocation

A strategy in which participants are randomly assigned to study arms of a clinical trial by computer.

Randomization number 

A unique number assigned to each randomized patient used to classify individuals but to maintain confidentiality, corresponding to a particular research arm assignment.

Run-in period 

The time elapsed until the study begins where no investigational medication is given to the trial participants. Patients may also receive standard treatments for their disease during this time, if these treatments are permitted within the trial period

Serious adverse event

An adverse event that is life-threatening, involves hospitalization or prolonged hospital stay, results in persistent or significant incapacity, induces congenital abnormalities or birth defects, or results in death.


The sponsor is the company or individual who manages several sites in the clinical trial.

Study completed date

The date on which the last research participant made the final visit to the site of the study (i.e. “last subject, last visit”) and the last samples were obtained or the last experiments were carried out.


An person (either a healthy volunteer or a patient volunteer) whose reactions or reactions to certain interventions are assessed during a clinical trial,  also be referred to as a trial participant.

Subject number

A specific number assigned to each person who is participating in a clinical trial.


Information obtained during the clinical trial from either direct or indirect data. For example, one variable might be “weight,” which would then be tested at specified time points in the trial.

Wash-out period

The period of time provided for the removal of all the drugs administered from the body.”


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