Clinical trial glossary

An established intervention used for comparison with the intervention being studied. It is different from an inactive placebo.

An unfavourable health event recorded during research. Recording an event does not by itself mean that the intervention caused it.

Keeping the study assignment unknown to specified people for a defined period. Double blind usually concerns participants and relevant investigators or assessors; the protocol explains who is blinded, rather than assuming every team member is unaware.

Control groups and placebo

Research involving people to understand health, care or illness. It includes interventional trials and observational research; a research record is not automatically a treatment trial.

Research that assigns people in advance to an intervention and evaluates health-related effects. Simply observing existing care or collecting a survey does not necessarily meet this definition.

What is a clinical trial?

A group used as a comparison. Depending on the protocol, it may receive usual care, another active intervention, placebo or another defined approach.

Conditions used by the research team to decide who can take part. Inclusion criteria describe required characteristics; exclusion criteria describe reasons participation may be unsuitable. A public list is not a personal eligibility decision.

Joining a study through its required process. Asking a question or leaving an email is not the same as being enrolled. In a registry record, enrolment can also mean the estimated or actual number of participants.

Planned contact or assessments after a study step, intervention or participation period. Ask about duration, responsibilities and whether follow-up differs from your ordinary care.

A person or organisation providing financial support. Funding alone does not necessarily make that organisation the study sponsor; check the responsibilities named in the record.

An ongoing process of understandable information, questions and voluntary choice about research. Signing a form can document a decision, but does not replace the discussion.

Understand research consent

An action or approach being evaluated, such as a medicine, talking therapy, device, digital tool or care programme. The category does not establish that it is effective.

Research that observes outcomes without researchers assigning the intervention under study. For example, researchers might follow people who already receive different forms of care.

A design in which the relevant people know which intervention participants receive. Knowing the assignment does not establish that the intervention will help.

A defined measurement used to assess a study question. The primary outcome is the main planned outcome; secondary outcomes address additional questions. A change on a rating scale is not automatically a meaningful improvement for every participant.

Payment may recognise time or inconvenience; reimbursement covers specified eligible expenses. A study can offer both, either or neither. These are separate from arrangements for research-related injury.

Payment and costs

In drug development, phases describe stages examining matters such as safety, dose and effects, with phase 4 after approval. The same phase labels do not apply uniformly to behavioural, device, digital or observational research.

An inactive comparison resembling the intervention, such as a tablet without the active study drug. Placebo is not the same as an active comparator or a sham procedure. It does not mean no care, no possible effects or that every trial uses one.

Placebo and comparison groups

The researcher responsible for leading the study or its work at a site, as specified in the record. The investigator is distinct from the wider team and from a sponsor, although responsibilities can sometimes overlap.

The study plan describing its questions, design, procedures and criteria. The participant information explains the practical implications; a public summary may not contain every detail.

Using chance to allocate participants to groups according to the protocol. Participants do not simply choose a group, and allocation need not put equal numbers in each group.

A record’s label for recruitment or progress. Recruiting may be open overall without places at your site. Active, not recruiting is not open to new participants; completed describes study progress, not a successful treatment. Confirm local availability.

A committee that reviews research ethics and participant protections within its jurisdiction. Examples include an institutional review board (IRB) in the US and a human research ethics committee (HREC) in Australia. Review does not make research risk-free.

A local centre or location involved in the study. An overall recruiting status does not establish that every listed site is open or practical for you.

Checking potential eligibility through the study’s specified process. Preliminary discussion and research-only screening procedures are different; the team must explain appropriate consent before research procedures.

Preparing for screening

An adverse event meeting specified seriousness criteria, such as death, a life-threatening event or hospitalisation. Seriousness concerns defined outcomes and is different from how severe or intense a symptom feels.

A comparison designed to resemble aspects of a procedure without its intended active component. Its design, possible effects and risks must be explained; it should not be assumed harmless.

The person or organisation responsible for initiating and managing a study and arranging its financing, as identified in its record. Providing funding alone does not necessarily make someone the sponsor. A sponsor-investigator can hold both sponsor and investigator roles.

A protocol-defined group receiving a particular intervention or comparison approach. A study can have one or several arms.

A reference identifying a study record. NCT numbers identify ClinicalTrials.gov records; other registries use other formats. An identifier is not a certification of safety, effectiveness, endorsement or your eligibility.

Stopping some or all further study participation. Ask about stopping procedures, care and follow-up, and separately about information already collected; withdrawal does not automatically erase every existing record.

Questions about leaving a study