Clinical trial terms
Understand common clinical trial terms used on Health Trials.
Sponsors/Collaborators
This shows who is responsible for the trial and making sure all trial information is correctly reported and updated. In some cases, the sponsor can assign a lead researcher or doctor to be responsible for the trial, as long as they have full control of the trial.
Collaborator
Other organizations that help with the trial, for example by providing funding, expertise, or support with running or analyzing the trial.
Principal Investigator
The main doctor or researcher in charge of running the trial and making sure it is carried out properly.
Sponsor
The person or organization that starts and manages the trial. They are responsible for planning, funding, and overseeing the research.
Sponsor-Investigator
A person who both starts the trial and is also responsible for running it.
| Term | Description |
|---|---|
| Collaborator | Other organizations that help with the trial, for example by providing funding, expertise, or support with running or analyzing the trial. |
| Principal Investigator | The main doctor or researcher in charge of running the trial and making sure it is carried out properly. |
| Sponsor | The person or organization that starts and manages the trial. They are responsible for planning, funding, and overseeing the research. |
| Sponsor-Investigator | A person who both starts the trial and is also responsible for running it. |
Trial status
The trial status shows whether a trial is currently looking for participants.
Active, not recruiting
The trial is still ongoing, but no longer accepting new participants. People who have already joined continue in the trial.
Approved for marketing
The treatment has been approved and is available for use. The trial is no longer recruiting participants.
Available
The treatment may be available to eligible patients. Contact the trial team to learn if you qualify.
Completed
The trial has ended as planned. No new participants can join at this stage.
Enrolling by invitation
The trial is only open to people who are invited by the trial team.
No longer available
The trial is no longer available for participation.
Not yet recruiting
The trial is not yet open for participation.
Recruiting
The trial is currently looking for participants. If you meet the criteria, you may be able to join.
Suspended
The trial has been temporarily paused. No new participants can join right now, but the trial may start again later.
Temporarily not available
The treatment or trial is temporarily unavailable. It may become available again in the future.
Terminated
The trial ended earlier than planned and will not continue. Participants can no longer join.
Unknown
The current trial status has not been updated or cannot be confirmed.
Withdrawn
The trial was stopped before any participants joined.
Withheld
Information about the trial status is not publicly available.
| Term | Description |
|---|---|
| Active, not recruiting | The trial is still ongoing, but no longer accepting new participants. People who have already joined continue in the trial. |
| Approved for marketing | The treatment has been approved and is available for use. The trial is no longer recruiting participants. |
| Available | The treatment may be available to eligible patients. Contact the trial team to learn if you qualify. |
| Completed | The trial has ended as planned. No new participants can join at this stage. |
| Enrolling by invitation | The trial is only open to people who are invited by the trial team. |
| No longer available | The trial is no longer available for participation. |
| Not yet recruiting | The trial is not yet open for participation. |
| Recruiting | The trial is currently looking for participants. If you meet the criteria, you may be able to join. |
| Suspended | The trial has been temporarily paused. No new participants can join right now, but the trial may start again later. |
| Temporarily not available | The treatment or trial is temporarily unavailable. It may become available again in the future. |
| Terminated | The trial ended earlier than planned and will not continue. Participants can no longer join. |
| Unknown | The current trial status has not been updated or cannot be confirmed. |
| Withdrawn | The trial was stopped before any participants joined. |
| Withheld | Information about the trial status is not publicly available. |
Trial phase
The trial phase shows how far along a treatment is in testing, from early research to large trials and follow-up trials after approval.
Early Phase 1
An initial, small trial in humans. The focus is to explore how the body responds, often using very low doses. It is not intended to treat or diagnose a condition.
N/A
This trial has no formal phase. This is common for trials of devices, procedures, or behavioral trials.
Phase 1
The first step of testing a treatment in people. The focus is on safety, side effects, and how the body responds to the treatment.
Phase 1/2
A combined trial that looks at both safety and effectiveness.
Phase 2
A combined trial that is testing how well a treatment works and continues to test it in larger groups to confirm the results.
Phase 2/3
A combined trial that is testing how well a treatment works and continues to test it in larger groups to confirm the results.
Phase 3
A large trial that checks how well a treatment works and how safe it is by comparing it to standard care or no treatment (placebo).
Phase 4
A trial done after treatment is approved. The focus is to see how the treatment works over time in everyday use, including long term benefits and safety.
| Term | Description |
|---|---|
| Early Phase 1 | An initial, small trial in humans. The focus is to explore how the body responds, often using very low doses. It is not intended to treat or diagnose a condition. |
| N/A | This trial has no formal phase. This is common for trials of devices, procedures, or behavioral trials. |
| Phase 1 | The first step of testing a treatment in people. The focus is on safety, side effects, and how the body responds to the treatment. |
| Phase 1/2 | A combined trial that looks at both safety and effectiveness. |
| Phase 2 | A combined trial that is testing how well a treatment works and continues to test it in larger groups to confirm the results. |
| Phase 2/3 | A combined trial that is testing how well a treatment works and continues to test it in larger groups to confirm the results. |
| Phase 3 | A large trial that checks how well a treatment works and how safe it is by comparing it to standard care or no treatment (placebo). |
| Phase 4 | A trial done after treatment is approved. The focus is to see how the treatment works over time in everyday use, including long term benefits and safety. |
Trial type
The trial type describes how the research is done, whether participants are given a treatment or simply observed.
Expanded Access
A way for some patients who cannot join a clinical trial to get access to an experimental treatment. This is only for special cases and is not part of a research trial.
Interventional
A trial where participants are given a treatment or intervention to see how it affects their health.
Observational
A trial where researchers simply observe and record what happens. They do not assign any treatment or change care. Instead, they collect information to better understand health patterns and outcomes.
Pivotal trial
Typically a phase 3 clinical trial, designed to show whether a treatment works and is safe enough for approval by health authorities.
| Term | Description |
|---|---|
| Expanded Access | A way for some patients who cannot join a clinical trial to get access to an experimental treatment. This is only for special cases and is not part of a research trial. |
| Interventional | A trial where participants are given a treatment or intervention to see how it affects their health. |
| Observational | A trial where researchers simply observe and record what happens. They do not assign any treatment or change care. Instead, they collect information to better understand health patterns and outcomes. |
| Pivotal trial | Typically a phase 3 clinical trial, designed to show whether a treatment works and is safe enough for approval by health authorities. |
Trial description
These terms explain the different levels of information used to describe what a trial is about.
Brief summary
A short overview of what the trial is about, written for the general public.
Detailed description
A longer and often more technical explanation of the trial, how it is carried out, and what researchers are studying.
| Term | Description |
|---|---|
| Brief summary | A short overview of what the trial is about, written for the general public. |
| Detailed description | A longer and often more technical explanation of the trial, how it is carried out, and what researchers are studying. |
Eligibility
These terms explain who may be able to join a trial and where participants may be selected from.
Eligibility criteria
The requirements a person must meet to join a trial, such as age, condition, or medical history.
Healthy volunteers
People who do not have the condition being studied but may still be allowed to take part in the trial.
Trial population
For observational trials, the group of people researchers plan to select participants from, such as patients at a clinic or people in a community.
| Term | Description |
|---|---|
| Eligibility criteria | The requirements a person must meet to join a trial, such as age, condition, or medical history. |
| Healthy volunteers | People who do not have the condition being studied but may still be allowed to take part in the trial. |
| Trial population | For observational trials, the group of people researchers plan to select participants from, such as patients at a clinic or people in a community. |
Design model
The design model describes how participants are organized, assigned, or followed during a trial.
Case-control
People with a particular condition or outcome are compared with similar people who do not have it.
Case-crossover
The same participants are compared at different periods of time, such as shortly before a health event and at an earlier time.
Case-only
One group of people with a particular condition or characteristic is studied.
Cohort
A group of people with something in common is followed to learn how their health or other characteristics change over time.
Crossover
Participants receive different interventions at different times, so the same person may receive more than one intervention during the trial.
Ecologic or community
Whole populations or communities are compared using factors such as environment, healthcare, lifestyle, or disease rates.
Factorial
Two or more interventions are tested separately and in combination to compare their effects.
Family-based
The trial focuses on related people, such as family members or twins.
Other
The trial uses another observational design that does not fit the standard categories.
Parallel
Participants are placed into two or more groups that are followed at the same time, usually receiving different interventions or care.
Sequential
New groups or treatment steps are decided as the trial progresses based on earlier results or milestones.
Single group
All participants are placed in one group rather than being divided into separate comparison groups.
| Term | Description |
|---|---|
| Case-control | People with a particular condition or outcome are compared with similar people who do not have it. |
| Case-crossover | The same participants are compared at different periods of time, such as shortly before a health event and at an earlier time. |
| Case-only | One group of people with a particular condition or characteristic is studied. |
| Cohort | A group of people with something in common is followed to learn how their health or other characteristics change over time. |
| Crossover | Participants receive different interventions at different times, so the same person may receive more than one intervention during the trial. |
| Ecologic or community | Whole populations or communities are compared using factors such as environment, healthcare, lifestyle, or disease rates. |
| Factorial | Two or more interventions are tested separately and in combination to compare their effects. |
| Family-based | The trial focuses on related people, such as family members or twins. |
| Other | The trial uses another observational design that does not fit the standard categories. |
| Parallel | Participants are placed into two or more groups that are followed at the same time, usually receiving different interventions or care. |
| Sequential | New groups or treatment steps are decided as the trial progresses based on earlier results or milestones. |
| Single group | All participants are placed in one group rather than being divided into separate comparison groups. |
Time perspective
Time perspective describes when observations are collected in relation to when participants join an observational trial.
Cross-sectional
Information is collected at one point in time, usually around when participants join the trial.
Other
The trial uses another timing approach that does not fit the standard categories.
Prospective
Researchers follow participants forward in time and collect information after they join the trial.
Retrospective
Researchers mainly look back at information that was collected before participants were selected or joined the trial.
| Term | Description |
|---|---|
| Cross-sectional | Information is collected at one point in time, usually around when participants join the trial. |
| Other | The trial uses another timing approach that does not fit the standard categories. |
| Prospective | Researchers follow participants forward in time and collect information after they join the trial. |
| Retrospective | Researchers mainly look back at information that was collected before participants were selected or joined the trial. |
Trial groups
These terms explain how participants may be grouped and the role each group has in the trial.
Active comparator
A group that receives an existing active treatment so it can be compared with the treatment being studied.
Arm/trial group
A group of participants studied together, often because they receive the same intervention or share similar characteristics.
Experimental treatment
A group that receives the intervention being tested in the trial.
No intervention
A group that does not receive a trial intervention.
Other
A trial group whose role does not fit one of the standard group types.
Placebo comparator
A group that receives a placebo so researchers can compare it with the active intervention.
Sham comparator
A group that receives a procedure or device designed to resemble the real intervention without providing its active effect.
| Term | Description |
|---|---|
| Active comparator | A group that receives an existing active treatment so it can be compared with the treatment being studied. |
| Arm/trial group | A group of participants studied together, often because they receive the same intervention or share similar characteristics. |
| Experimental treatment | A group that receives the intervention being tested in the trial. |
| No intervention | A group that does not receive a trial intervention. |
| Other | A trial group whose role does not fit one of the standard group types. |
| Placebo comparator | A group that receives a placebo so researchers can compare it with the active intervention. |
| Sham comparator | A group that receives a procedure or device designed to resemble the real intervention without providing its active effect. |
Interventions
These terms explain the treatments, procedures, tests, or other approaches being studied.
Behavioral
An approach designed to change behavior, lifestyle, or mental health, such as counseling or psychotherapy.
Biological/Vaccine
A biological treatment or vaccine being studied.
Combination product
An intervention that combines different product types, such as a drug and a medical device.
Device
A medical device, or sometimes a sham device used for comparison, that is being studied.
Diagnostic test
A test used to detect or assess a condition, such as imaging or a laboratory test.
Dietary supplement
A supplement being studied, such as vitamins or minerals.
Drug
A medicine being studied. This category can also include a placebo used for comparison.
Genetic
An intervention involving genes, gene transfer, stem cells, or related genetic techniques.
Intervention
A treatment, procedure, test, or other approach being studied.
Intervention description
More details about how an intervention is given or used, such as the dose, frequency, or duration.
Other intervention
An intervention that does not fit one of the standard intervention types.
Procedure/Surgery
A medical or surgical procedure being studied.
Radiation
An intervention that uses radiation as part of the treatment being studied.
| Term | Description |
|---|---|
| Behavioral | An approach designed to change behavior, lifestyle, or mental health, such as counseling or psychotherapy. |
| Biological/Vaccine | A biological treatment or vaccine being studied. |
| Combination product | An intervention that combines different product types, such as a drug and a medical device. |
| Device | A medical device, or sometimes a sham device used for comparison, that is being studied. |
| Diagnostic test | A test used to detect or assess a condition, such as imaging or a laboratory test. |
| Dietary supplement | A supplement being studied, such as vitamins or minerals. |
| Drug | A medicine being studied. This category can also include a placebo used for comparison. |
| Genetic | An intervention involving genes, gene transfer, stem cells, or related genetic techniques. |
| Intervention | A treatment, procedure, test, or other approach being studied. |
| Intervention description | More details about how an intervention is given or used, such as the dose, frequency, or duration. |
| Other intervention | An intervention that does not fit one of the standard intervention types. |
| Procedure/Surgery | A medical or surgical procedure being studied. |
| Radiation | An intervention that uses radiation as part of the treatment being studied. |
Trial outcomes
These terms explain what researchers measure to evaluate what happens during a trial.
Other outcome
Another planned measurement used in the trial that is not classified as a primary or secondary outcome.
Outcome time frame
When, or over what period of time, an outcome is measured for each participant.
Primary endpoint/outcome
The main result the trial is designed to measure, such as whether a treatment improves symptoms or slows disease.
Secondary outcome
An additional planned result or measurement that helps answer other important questions but is not the main outcome of the trial.
| Term | Description |
|---|---|
| Other outcome | Another planned measurement used in the trial that is not classified as a primary or secondary outcome. |
| Outcome time frame | When, or over what period of time, an outcome is measured for each participant. |
| Primary endpoint/outcome | The main result the trial is designed to measure, such as whether a treatment improves symptoms or slows disease. |
| Secondary outcome | An additional planned result or measurement that helps answer other important questions but is not the main outcome of the trial. |
Trial contacts
These terms explain who patients can contact with questions about joining or taking part in a trial.
Trial contact
A person who can answer questions about joining the trial across any of its locations.
Site contact
A person at a specific trial location who can answer questions about the trial or joining at that site.
| Term | Description |
|---|---|
| Trial contact | A person who can answer questions about joining the trial across any of its locations. |
| Site contact | A person at a specific trial location who can answer questions about the trial or joining at that site. |
Other terms
These terms describe common features, methods, and measurements used in clinical trials.
Adverse events
Any unwanted health problems that occur during a trial, whether or not they are caused by the treatment.
Blinded trial
A trial where participants do not know which treatment each person receives, to keep results unbiased.
Double blinded
When both participants and researchers do not know which treatment each person receives, to keep results unbiased.
Enrollment/sample size
The number of people who are planned to take part in the trial.
Placebo
A substance or treatment with no active medicine, used for comparison to see if the real treatment works.
Protocol
The detailed plan for how the trial is conducted, including who can join, what treatments are given, and what is measured.
Randomized
Participants are assigned to different treatments by chance, like flipping a coin.
| Term | Description |
|---|---|
| Adverse events | Any unwanted health problems that occur during a trial, whether or not they are caused by the treatment. |
| Blinded trial | A trial where participants do not know which treatment each person receives, to keep results unbiased. |
| Double blinded | When both participants and researchers do not know which treatment each person receives, to keep results unbiased. |
| Enrollment/sample size | The number of people who are planned to take part in the trial. |
| Placebo | A substance or treatment with no active medicine, used for comparison to see if the real treatment works. |
| Protocol | The detailed plan for how the trial is conducted, including who can join, what treatments are given, and what is measured. |
| Randomized | Participants are assigned to different treatments by chance, like flipping a coin. |