Clinical research participation glossary

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Adverse event (AE)

An unfavorable medical occurrence collected during the protocol-defined reporting period. In drug trials, an event may be temporally associated with use of the product without being caused by it. Follow the study’s reporting instructions; the team evaluates relationship and expectedness.

Allocation

The method used to assign participants to study arms. Randomized allocation uses chance. Nonrandomized allocation follows another stated method.

Arm

A participant group that receives a defined intervention, comparator, sequence, or observation plan.

Assent

Affirmative agreement from a person who is not legally able to provide full informed consent, often used with permission from a parent or legally authorized representative when required.

Baseline

Measurements collected before an intervention or defined study period, used as a comparison point.

Bias

A systematic influence that can distort study design, conduct, analysis, or interpretation. Randomization, masking, and prespecified outcomes can reduce selected forms of bias.

Biospecimen

A biological sample such as blood, tissue, saliva, urine, or stool collected for testing, storage, or future research under the study’s permissions.

Blinding or masking

A design feature that limits who knows the assigned intervention. Read the named roles; labels such as single or double masking can hide important differences.

Clinical trial

An interventional research study in people that prospectively assigns one or more health-related interventions to evaluate effects on health outcomes.

CLIA

The Clinical Laboratory Improvement Amendments establish U.S. quality standards for laboratories testing human specimens to assess health or to diagnose, prevent, or treat disease. CMS explains (opens in a new tab) that research laboratories may qualify for an exception when they do not report patient-specific results or use results to change treatment.

Cohort

A defined group enrolled or analyzed together. Early-phase trials may open dose cohorts in sequence.

Comparator

The intervention, placebo, standard care, or other condition against which another arm is evaluated.

Consent form

A document used to present and record consent information when documentation is required. The informed consent process includes discussion, questions, and updates throughout participation.

Contract research organization (CRO)

A company that performs study duties for a sponsor, such as monitoring, data management, site support, or other operations.

Crossover

A design in which participants receive more than one intervention in a sequence, often with a washout between periods.

Decentralized clinical trial

A study that performs some or all activities away from a traditional research site through telehealth, home visits, local providers, apps, devices, or shipping.

Coded, pseudonymized, and de-identified data

Coded or pseudonymized data replace direct identifiers with a code that an authorized party may be able to reconnect. De-identified data meet a stated legal or technical standard intended to prevent identification. Ask which term and standard apply, who holds any key, and what re-identification limits remain.

Endpoint or outcome measure

A prespecified measurement used to answer a research question. An endpoint does not establish that an intervention benefits an individual participant.

Expanded access

A pathway that may allow certain patients to receive an investigational product outside a clinical trial when applicable criteria and authorizations are met.

HIPAA authorization

Permission for a covered entity to use or disclose protected health information for a stated purpose when HIPAA applies. It differs from consent to participate, though both can appear in one document.

Incidental finding

A finding discovered during research that lies outside the study’s main question. The protocol and consent should describe whether and how selected findings are evaluated or returned.

Inclusion criteria

Characteristics a person must have to qualify under the protocol.

Exclusion criteria

Characteristics that prevent participation under the protocol because of safety, study design, data interpretation, or operational requirements.

Informed consent

An ongoing process in which research information is communicated so a person can decide freely whether to participate and can continue to ask questions and reconsider.

Institutional review board (IRB)

A committee that reviews covered research involving people, including risk, consent, subject selection, privacy, and safeguards. Approval does not prove that an intervention works or fits a specific person.

Investigational product

A drug, biologic, device, or other product studied under a protocol. It may be unapproved or used in an unapproved way.

Legally authorized representative (LAR)

A person authorized under applicable law to consent on behalf of a prospective participant in defined circumstances.

NCT number

The identifier assigned to a study record registered on ClinicalTrials.gov. It identifies a record; it does not endorse a recruiter or guarantee that a location is open.

Observational study

Research that assesses outcomes without prospectively assigning participants to a health-related intervention under the study design.

Open label

A design in which assigned intervention information is known to participants and investigators, subject to the protocol.

Pharmacodynamics (PD)

What a drug does to the body or biological system, measured through effects or biomarkers.

Pharmacokinetics (PK)

How a drug is absorbed, distributed, metabolized, and eliminated, often studied through timed blood or other samples.

Phase

A development stage used for many drug and biologic trials. Phase 1 often examines safety, dose, and PK; Phase 2 adds preliminary effectiveness and safety; Phase 3 evaluates benefit and risk in larger groups; Phase 4 occurs after approval. Designs vary.

Placebo

A comparator designed to resemble the intervention without its active component. Read what standard care continues, what rescue treatment is available, and whether assignment is masked.

Principal investigator (PI)

The investigator responsible for conducting a study at a site or under a protocol, depending on the research structure.

Primary completion date

The date when the final participant was examined or received an intervention for final collection of data for the primary outcome measure. This registry milestone can occur after your own final visit.

Protocol

The approved study plan that defines objectives, design, eligibility, interventions, procedures, data collection, analysis, and safety management.

Protocol deviation

A departure from the approved protocol. The study documents, reviews, and reports deviations according to applicable requirements and policy.

Randomization

Assignment by chance to a study arm according to a planned method. Ask for the assignment ratio and whether it changes by cohort or stage.

Rescue medication

Treatment allowed by the protocol to address symptoms or clinical worsening under defined conditions.

Routine patient costs

A term used in clinical-trial insurance rules for defined items and services that would otherwise be covered outside the trial or arise from covered care. The exact definition, exclusions, network rules, and cost sharing depend on the governing coverage rule and health plan.

Serious adverse event (SAE)

An adverse event meeting regulatory outcome criteria such as death, a life-threatening event, hospitalization or prolonged hospitalization, persistent or significant disability or permanent damage, congenital anomaly or birth defect, or another important medical event that may require intervention. Seriousness differs from intensity.

Sentinel dosing

A safety approach in which one or a small number of participants receive an intervention before the rest of a cohort, followed by a planned observation or review period.

Sponsor

The person or organization that initiates and takes responsibility for a clinical investigation. The sponsor may delegate duties while retaining defined responsibilities.

Study completion date

The date when the final participant was examined or received an intervention for final collection of data for the primary and secondary outcome measures and adverse events under the registry definition.

Study-related injury

An illness, injury, or complication that a study process identifies as related to research participation under its terms. Ask who determines relatedness, which care and costs qualify, and which review process applies.

Washout

A protocol-defined period intended to reduce effects of a prior drug or intervention before another study period. Never stop medication or calculate a washout without qualified guidance.

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Use definitions as a starting point

A protocol can define an operational term more narrowly than a general glossary. Ask the research team how a term changes what you receive, do, report, pay, or consent to. Save the answer beside the source document and version.