How do Clinical Trials Work?

How do Clinical Trials work and who is involved and who can participate?

Clinical trials are research studies that aim to determine whether a medical strategy, treatment, or device is safe for use or consumption by humans. To ensure participant safety, trials start with small groups and examine whether a new method causes any harm or unsatisfactory side effects. This is because a technique that is successful in a laboratory or in animals may not be safe or effective for humans.

Fast facts on clinical trials

  • Clinical trials aim to find out whether a medical strategy, treatment, or device is safe and effective for humans to use or consume.
  • Trials consist of four phases, and they can focus on: treatment, prevention, diagnostic, screening, supportive care, health services research, and basic science.
  • A research team will likely include doctors, nurses, social workers, health care professionals, scientists, data managers, and clinical trial coordinators.
  • Participation can involve both risks and benefits. Participants must read and sign the “informed consent” document before joining a trial.
  • Risks are controlled and monitored, but the nature of medical research studies means that some risks are unavoidable.

Clinical trials on humans occur in the final stages of a long, systematic, and thorough research process. The process often begins in a laboratory, where new concepts are developed and tested. Testing on animals enables scientists to see how the approach affects a living body. Finally, human testing is carried out in small and then larger groups.

Trials may be carried out to:

  • Evaluate one or more treatment interventions for a disease, syndrome or condition, such as drugs, medical devices, or approaches to surgery or therapies
  • Assess ways to prevent a disease or condition, for example, through medicines, vaccines, and lifestyle changes
  • Evaluate one or more diagnosis interventions that might identify or diagnose a particular disease or condition
  • Examine identification methods for recognizing a condition or risk factors for that condition
  • Explore supportive care procedures to improve the comfort and quality of life of people with a chronic illness

The outcome of a clinical trial may identify if a new medical strategy, treatment or device: 

  • has a positive effect on patient prognosis
  • causes unforeseen harm
  • has no positive benefits or has negative effects

Types of clinical trial

All clinical trials have a primary purpose. These can be broken down into the following categories:

  • Treatment: Testing new treatments, new drug combinations, or new approaches to surgery or therapy
  • Prevention: Examining ways to improve prevention or recurrence of disease through, for example, medicines, vitamins, vaccines, minerals, and lifestyle changes
  • Diagnostic: Finding improved testing techniques and procedures for diagnosing diseases and conditions
  • Screening: Testing the best method of identifying certain diseases or health conditions
  • Supportive care: Investigating procedures to improve comfort and quality of life for patients with a chronic condition
  • Health services research: Evaluating the delivery, process, management, organization, or financing of health care
  • Basic science: Examining how an intervention works

Why are clinical trials important?

Clinical trials help improve and advance medical care. The studies provide factual evidence that can be used to improve patient care.

Clinical research is only conducted if doctors are unaware of elements such as:

  •     whether a new approach works effectively in humans and is safe
  •     what treatments or strategies work most successfully for certain illness and groups of individuals

How do clinical trials work?

Various elements are involved in setting up, running, and following up a clinical trial.

Clinical trials protocol:

A trial follows a comprehensive plan or protocol. A protocol is the written description of a clinical trial. It includes the study’s objectives, design and methods, relevant scientific background, and statistical information.

Key information to include may be:

  • the number of participants
  • who is eligible to take part
  • what tests will be given and how often
  • types of data to be collected
  • the length of the study
  • detailed information about the treatment plan

Avoiding bias

Researchers must take measures to avoid bias.

Bias refers to human choices or other factors that are not related to the protocol but which may affect the results of the trial.

Steps that can help to avoid bias are comparison groups, randomization, and masking.

Comparison groups

Most clinical trials use comparison groups to compare medical strategies and treatments. Results will show if one group has a better outcome than the other.

This is usually conducted in one of two ways:

  • One group receives an existing treatment for a condition, and the second group receives a new treatment. Researchers then compare which group has better results.
  • One group receives a new treatment, and the second group receives a placebo, an inactive product that looks like the test product.


Clinical trials with comparison groups often use randomization. Participants are allocated to comparison groups by chance rather than by choice. This means that any differences seen during a trial will be due to the strategy used and not because of pre-existing differences between participants.

Masking or blinding

Masking or blinding helps avoid bias by not informing either the participants or the researchers which treatment the participants will be receiving.

Single-blind: This is when either the participants or researchers are unaware, of which group is which.

Double-blind: This is when both participants and researchers are unaware.

Who is involved in a clinical trial?


The sponsor of a clinical trial may be a pharmaceutical company, research institution – anyone who is willing to take the responsibility to manage or finance a clinical trial.

Any government agency can also play a role as a sponsor.

Role of Sponsor

  • Responsible for selecting the investigator(s).
  • Provide the investigator(s)/institution(s) with the protocol and an up-to-date Investigator’s Brochure. 
  • Obtain the investigator’s agreement to conduct the trial in accordance with GCP, protocol, and regulatory requirements. 


While drug developers are an essential aspect of clinical research, they may not have the experience or manpower to find patients, collect data and navigate the FDA approval process.  This is where “Contract Research Organizations” come in and provide outsourced support to the clinical research process by offering services and assistance in conducting clinical trials. 

Trial Site: 

  • Location where trial-related activities are actually conducted.
  • The first and foremost criteria of selection of trial site should always be the site’s ability to gather high quality data.
  • Sponsor should be diligent in selecting the appropriate trial site.


Each clinical trial requires a clinical investigator who is qualified by training and experience to be an appropriate expert to investigate the drug and monitor the patient.

Role of Investigator: 

  • Primary responsibility is to be diligent in conducting research in an ethical manner that contributes to generalize knowledge while protecting the rights and welfare of study participants. 
  • To comply with procedures for data recording/reporting.
  • To permit monitoring, auditing and inspection.

Study Participants:  

Individuals who participate in human subject research by being the target of observation by researchers.

Institutional Review Board (IRB):

 A group formally designated to protect the rights, safety and well-being of humans involved in a clinical trial by reviewing all aspects of the trial and approving its start-up. IRB’s can also called as “Independent Ethics Committees” and constitutes medical, scientific, and non-scientific members.

Food and Drug Administration:

Agency which mainly focusses on the health and well-being of the human subjects who are participating in the study.

  • FDA regulations are in place to guarantee that all drugs that receive final approval are safe and effective.

Data Monitoring Committees (DMC): 

A group of individuals with pertinent expertise that reviews on a regular basis accumulating data from one or more ongoing clinical trials. 

  • The DMC advises the sponsor regarding the continuing safety of trial subjects and those yet to be recruited to the trial, as well as the continuing validity and scientific merit of the trial.

Who sponsors clinical trials?

Clinical trials and research can cost hundreds of millions of dollars. Groups that fund trials may include:

  •   pharmaceutical, biotechnology, and medical device companies
  •   academic medical centers
  •   voluntary groups and foundations
  •   National Institutes of Health
  •   government departments
  •   physicians and health providers
  •   Individuals

Who can participate?

The protocol defines who is eligible to participate in a trial.

The informed consent form (ICF): should be provided by all study participants in the trial.

  • After signing the ICF forms the participants enter the screening phase and are assessed for study eligibility criteria.
  • An informed Consent form is a process used by researchers to provide potential and enrolled participants with information about a clinical study.
  • This information helps people decide whether they want to enroll in the study.
  • The Informed Consent Process is intended to protect participants and provide risks and benefits of the study.

Clinical studies have standards outlining who can participate.

These standards are called “Eligibility Criteria” and are listed in the protocol. Some research studies seek participants who have illnesses, other studies are looking for healthy participants.  Depending on their eligibility, participants are enrolled in the study.

Eligibility Criteria’s are classified into 2 types: 

  • Inclusion Criteria: The factors that allow someone to participate in a clinical study.
  • Exclusion Criteria: The factors that disqualify someone from participation.

They are based on factors such as age, gender, type of disease, history, etc.

  • Study participants who fail to meet the eligibility criteria’s are considered as “Screen Failures” and are excluded from the study.
  • If the study participant meets the eligibility criteria then that person proceeds to the randomization phase.
  • Randomization defines assigning the subjects into different arms (Treatment Groups).  
  • Study participants can be withdrawn from the study due to adverse event, protocol specified criteria or due to withdrawal of consent/investigator’s choice.

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