Clinical Trials Glossary

Clinical trials are research studies designed to test an investigational drug, medical device, or procedure to ensure they’re safe and effective. If you’re researching clinical trials and are interested in participating in one, you’ve likely come across a few terms you’re unfamiliar with as well. Familiarizing yourself with these terms can help you better prepare yourself and further your understanding of the clinical trials process.

Terms Used in Clinical Trials

Adverse Event (AE): A negative or undesirable experience that may or may not be caused by an investigational drug or procedure; also known as a negative reaction or side effect. AEs can occur during or within a certain amount of time after a trial has ended.

Arm Assignment: The assignment to a certain group (arm) in the clinical trial that receives an intervention or no intervention.

Assessment: A test or procedure, such as blood work or imaging tests, that is used for data collection purposes required by the clinical trial.

Background Therapy: The current standard of care given to treat a condition or disease.

Baseline: Measurements taken at the beginning of a clinical trial that provide a basis for the investigators to monitor changes. This serves as a reference point to compare measurements to throughout and at the end of the study. Baseline measurements can be taken from imaging, laboratory tests, and physical assessments.

Bias: A flaw in how data is collected or interpreted in a clinical trial that can lead to incorrect conclusions being made.

Blinding/Masking: A technique used in many clinical trials where the investigators, doctors, and/or the trial participants are unaware of which treatment or intervention they’re receiving. Blind clinical trials help prevent bias.

Case Report Form (CRF): A document that contains all information required by a protocol for a study.

Clinical Trial: A research study where one or more human subjects are divided into groups that receive either a placebo or intervention in order to determine the effects. These studies are used to determine how safe and effective the interventions are in treating medical conditions.

Clinical Research Coordinator (CRC): A member of the investigational team that handles day-to-day activities of the study. They may collect or review data and interact with patients in the study.

Concomitant Medication: Medication that participants take in addition to the intervention from the clinical trial. Some studies may not allow concomitant medications, as they could interfere with the results.

Confidentiality: The maintenance of participant privacy during a clinical trial, including names and all medical information. The FDA requires all studies to have a method for maintaining patient confidentiality throughout the study.

Clinical/Contract Research Organization (CRO): An organization hired by a pharmaceutical, medical device, or biotech company to manage all the functions required when conducting a clinical trial.

Control Group: The group in a clinical trial that doesn’t receive the study intervention. Instead, they receive a placebo (“fake” drug) or standard of care, depending on the disease or condition being studied.

Controlled Clinical Trial: A clinical trial where participants are divided into control and interventional groups.

Crossover Trial: A clinical trial where participants receive two or more interventions in a specific order. For example, group 1 may receive drug A first, and then drug B later — group 2 receives drug B first, and then drug A later.

Data and Safety Monitoring Board (DSMB): A group of people outside of a clinical trial that monitor data and results to help ensure participants’ safety throughout the study.

Dosing Discontinuation: The time when a study participant stops taking an investigational drug for any reason. This may be during or after the study is completed.

Double-Blind Trial: A type of clinical trial where both the medical staff and study participants don’t know if participants are receiving the control or intervention treatment.

Efficacy: Refers to whether a study intervention produces the desired effect for treating a condition or disease.

Electronic Data Capture (EDC): Computer software used to collect, organize, and process clinical trial data.

Exclusion Criteria: A list of conditions or medications that prevent a person from participating in a particular clinical trial.

Experimental Group: The group in a clinical trial that receives the intervention or treatment being studied, as opposed to the control group.

First-In-Human Study: A clinical trial that’s studying an investigational drug, medical device, or procedure for the first time in humans — typically refers to a phase 1 clinical trial.

Food and Drug Administration (FDA): A federal agency within the U.S. Department of Health and Human Services that’s responsible for monitoring drugs, medical devices, dietary supplements, cosmetics, and other health products for their safety and efficacy.

Healthy volunteer: A person without a condition or disease that volunteers to take part in a clinical trial. Healthy volunteers are often used in phase 1 clinical trials.

Health Insurance Portability and Accountability Act (HIPAA): The main federal law that protects the privacy of individuals’ health information. Among other things, it sets limits on how a person’s health records can be used and shared and sets security requirements for systems that store health information.

Inclusion Criteria: A list of conditions that are required to join a clinical trial.

Indication: The use of a treatment for a particular symptom, condition, or disease.

Informed Consent: The consent process required for enrolling in a clinical trial. In this process, the study investigator informs the participant about the study, the treatments they might  receive, any risks and benefits, and other relevant information. This process lets the participant know their rights, including that they can leave a clinical trial at any time for any reason.

Institutional Review Board (IRB): A board made up of scientists, doctors, researchers, and community members who monitor all human research to ensure it’s conducted ethically. Any study that receives federal funding is required to have an IRB.

Intervention: The investigational drug, medical device, or procedure being studied in a clinical trial.

Interventional Study: A clinical trial, where participants receive one or more interventions so that investigators can study their effects — as opposed to an observational study.

Investigational Drug: A new drug being studied in a clinical trial that’s not yet available to the public.

Investigational Group: The group in a clinical trial that  receives the study intervention, as opposed to the control group.

Investigational New Drug (IND) Application: An application submitted to the FDA for an investigation drug that allows investigators to begin clinical trials. An IND contains data from preclinical studies in cells and animal models to prove that it’s ready to test in humans.

Observational Study: A study that monitors health outcomes in people who receive their treatments as part of regular medical care and not in a clinical trial. These studies simply “observe” the effects as people continue with their daily lives.

Outcome Measure: A measurement that’s set in a protocol before a clinical trial begins that investigators use to determine how well an intervention works.

Observational Study Monitoring Board (OSMB): The safety board for observational studies that monitors vulnerable or large populations to ensure safety standards are being met.

Office for Human Research Protection: An agency within the Department of Health and Human Services that protects the rights of people participating in research studies funded by the federal government.

Open-Label Trial: A clinical trial where the medical staff, investigators, and participants know which intervention the participant is receiving.

Participant: An individual who has agreed to be in a clinical trial as a subject and who may either receive the intervention being studied or be part of a control group.

Phase: The stage of a clinical trial. In order for a drug, medical procedure, or device to be approved by the FDA, it has to go through three phases of clinical trials:

  • Phase 1 — a small study, typically using healthy volunteers, that looks at the safety and dosing of a drug
  • Phase 2 — a larger study of people with the condition or disease being studied who receive either a placebo or intervention, used to determine safety and efficacy
  • Phase 3 — a much larger study of people with the condition or disease being studied who also receive either a placebo or intervention to further determine safety and efficacy
  • Phase 4 — used to monitor the long-term safety of a drug after it’s approved by the FDA

Placebo: A “fake” drug that contains an inactive liquid or powder that looks identical to the intervention being given in a trial. It’s used as a comparison to determine how well an intervention works. A placebo doesn’t have any treatment value.

Principal Investigator (PI): The lead investigator for a clinical trial, typically a doctor who’s an expert in the condition or disease being treated. They’re in charge of the technical and scientific decisions being made during a study.

Protocol: A written study plan for a clinical trial that outlines the treatments being given, who can participate, the required medical tests and procedures, and outcome measures.

Randomization: The process of randomly assigning clinical trial participants to a control or interventional group to help reduce bias.

Safety Officer (SO): A doctor outside of a clinical trial that monitors safety and data collection in clinical trials running at only one site.

Screening Process: The process in which prospective study participants are asked questions to determine if they qualify for a clinical trial.

Sham Comparator Arm: An arm of a study in which the participants undergo a procedure that appears to be the same as the procedure being studied (such as a surgery) but that did not actually involve the active process being studied.

Standard of Care: The recommended treatment or procedures for a certain condition or disease that can be used in place of a placebo in cases where receiving a “fake” treatment would be unethical. For example, cancer patients in a control group typically receive a standard of care as opposed to a placebo.

Standard Operating Procedures (SOPs): Detailed instructions for a clinical trial that are used to keep the same standards across all clinical trial locations (sites).

Serious Adverse Events (SAEs): Adverse events that result in life-threatening complications, hospitalization, significant disability, birth defects in pregnant women, or death.

Sponsor: A person or organization funding a clinical trial with responsibility for regulatory compliance and ensuring that the trial is conducted with good clinical practices as defined by the FDA.

Stratification: Splitting up the groups in a clinical trial by specific characteristics, such as gender or age, so that investigators can determine if these characteristics affect the study results.

Subject: A person participating in a clinical trial — also known as a study participant or volunteer.

Subinvestigator: An individual designated and supervised by the investigator to perform specific duties during the clinical trial, such as assisting in monitoring of the subjects during the course of the study.

Unblinding/Unmasking: A point in the clinical trial where the investigators, doctors/nurses, and/or participants find out which treatment the participants received.

Wash-Out Period: The period of time it takes for an administered drug to be cleared from the body. Some clinical trials require a wash-out period of certain medications before a participant can begin the study.