A Guide to Understanding Clinical Trials

Clinical trials are studies with human volunteers that test how well a treatment works and if it’s safe. It is important that people from different backgrounds (race, ethnicity and sex) participate to see how treatments affect these groups. Volunteers are told about the possible risks before starting the trial. Before a clinical trial can begin for a treatment, medication or device, it must show promising results in laboratory or animal tests.

Below are some common questions about clinical trials.

What happens during a clinical trial?

At the beginning of a trial, a team of doctors, nurses, social workers and other health professionals:

• Checks the health of the proposed participants
• Identifies those who are eligible for the trial
• Gives specific instructions for using the treatment, medication or device during the trial

Participants sign an informed consent form before enrollment. Informed consent provides you with key information about the trial before you enroll. You will be asked to read the informed consent form, so you are fully aware of the study. You will be able to ask the investigators questions about the study. The team monitors the participants as the trial progresses. They also stay in touch for a week or two after the trial ends. All trials follow a plan called a protocol, which includes information on the length of the study and what information will be gathered. This plan is approved by an Institutional Review Board, or IRB.  

Are clinical trials safe?

For the most part, yes. However, sometimes investigational medications for specific conditions may have more risks. Participants are told about potential risks and benefits in the informed consent document. All U.S. trials must be approved and monitored by an IRB to ensure they are ethical and participants’ rights are protected.

Who can participate?

All trial protocols include definitions of who can participate. Eligibility depends on what is included in the study protocol. Criteria may include:

• Age
• Sex
• Type and stage of a disease
• Previous treatment history
• Other medical conditions

Some participants may be healthy volunteers who serve as control groups.

Why participate?

Your participation helps advance medical research. You will also have access to new treatments before they are widely available.

Do I have to stay in a hospital or leave my home?

Participants usually have regular visits at an accessible clinical trial site, such as a:

• Health care professional’s office
• University medical center
• Community hospital
• Clinic

Some trials may require some overnight stays or more frequent visits than normal for a condition. Many involve a physical exam or medical history review before enrollment. The participant should be given a description of what’s expected of them before signing the informed consent.

What kind of paperwork is involved?

The risks and potential benefits will be explained by a research team member. This information is also provided in the informed consent document. The participant must sign the document before taking part in the trial. According to the National Institutes of Health, the minimum required elements of informed consent include:

1. Activity being conducted
2. Purpose and length of research
3. Study procedures, including those that are experimental
4. Foreseeable risks
5. Potential benefits
6. Disclosure of alternative procedures or treatments
7. Confidentiality
8. Compensation (including when none is offered)
9. Course of action if more than minimal risk is involved
10. Who to contact for questions or research-related injury
11. Participation is voluntary
12. Disclaimer about the use of identifiable private information or specimens

Can you quit after a clinical trial starts?

Entering a clinical trial is voluntary. You may stop at any time without giving a reason. The informed consent document will discuss this further.

How long do trials usually last?

They vary greatly. Some clinical trials last just a few days, while others take years.

How do I prepare for a clinical trial?

You should learn as much about the trial as possible before reading and signing the informed consent. Ask questions such as:

• What is the purpose of the study?
• Why do researchers believe the treatment being tested may be effective? Has it been tested before?
• Who has reviewed and approved the study?
• What are the possible risks, side effects and benefits of the treatment?
• What other options do people with my condition have?
• How might this trial affect my daily life?
• How long will the trial last?
• What will be my responsibilities if I participate?
• What kinds of tests and treatments are involved?
• Will they hurt? If so, for how long?
• Will I be able to take my regular medications while in the trial?
• Will hospitalization be required?
• Who will pay for the treatment, or who is sponsoring the trial?
• Will I be paid for other expenses such as travel or childcare costs?
• Who can help answer questions from my insurance company or health plan?
• What type of long-term follow-up care is part of this study?
• How will I know that the treatment is working? Will I be provided with the results of the trials?
• Who will oversee my care?

Where can I find definitions of some scientific terms used during a clinical trial?

The National Institutes of Health Clinical Trials Glossary(link opens in new window) lists many terms commonly used in clinical trials.

Where can I get more detailed information about clinical trials?

Other sources include:

• ClinicalTrials.gov(link opens in new window)
• CenterWatch(link opens in new window)
• Office for Human Research Protections(link opens in new window)
• National Institutes of Health(link opens in new window)
• National Institutes of Health HIPAA Privacy Rule(link opens in new window)
• Research Match(link opens in new window)

How can I be sure a clinical trial is legitimate?

The sponsor (the organization that is sponsoring the study) or research coordinator should be able to answer your questions, such as:

• Whether the trial protocol is approved
• Will it be monitored by an IRB
• What is the purpose of the trial
• What are the possible risks
• How long the trial is expected to last

Another resource is the National Institutes of Health Clinical Trial Registry at http://clinicaltrials.gov(link opens in new window). This site lists trials in all 50 states and over 200 countries. You can search for a trial using criteria such as condition or disease treated, medication or therapy used or country. Each entry includes:

• Trial description
• Sponsors
• Purpose
• Estimated completion date
• Eligibility criteria
• Contact information

The World Health Organization International Clinical Trials Registry Platform(link opens in new window) provides similar information about trials worldwide.

What are the different types of clinical trials?

There are many kinds of trials, each with a different purpose:

• Behavioral trials look at ways behavior changes can improve health and outcomes. 
• Treatment trials test experimental treatments, new combinations of medications or new approaches to surgery or radiation therapy.
• Prevention trials look for better ways to prevent disease in people who have never had the disease or to prevent a disease from returning.
• Diagnostic trials assess tests or procedures for diagnosing a disease or condition.
• Screening trials look at methods of detecting a disease or condition.
• Quality of life trials (or supportive care trials) assess methods of improving the comfort and quality of life of patients with chronic illness.

Are there different phases of clinical trials?

To be approved by the U.S. Food and Drug Administration, an experimental medication or treatment must pass several phases of clinical trials.

• Phase I trials test an experimental medication or treatment in a small group of people (20-80) for the first time to evaluate its safety and identify side effects.
• Phase II trials test the experimental medication or treatment in a larger group of people (100-300) to learn its effectiveness and continue evaluating safety.
• Phase III trials test the experimental medication or treatment in a large group of people (1,000-3,000) to confirm its effectiveness, watch for side effects, compare it with standard or equivalent treatments and continue evaluating safety.
• Phase IV trials track more information about an experimental medication or treatment's safety and the best use after it has been approved by the FDA and made available to the public.

Who sponsors clinical trials?

Clinical trials can be sponsored by organizations or individuals, such as:

• Health care professionals
• Medical institutions
• Foundations
• Voluntary groups
• Pharmaceutical companies
• Federal agencies such as the National Institutes of Health, the Department of Defense and the Department of Veterans Affairs

What is a sponsor’s role?

• Selecting qualified investigators
• Securing IRB approval
• Providing funding or resources
• Monitoring the trial’s progress
• Reporting results to authorities

They do not conduct the research or interact with the participants.

Sponsors ensure the study is:

• Properly designed
• Ethically conducted
• Compliant with regulatory standards