Clinical trial glossary | Cure My Disease

Recruitment status

Whether a study is taking on new participants. Roughly ordered from easiest to join to furthest away.

Recruiting now: This trial is taking on new participants right now.
Not yet recruiting: Registered, but not yet taking participants.
By invitation only: Not open to general applications. Only people the study team invites can take part.
Paused: Paused for now. It may or may not start again.
Ongoing: Running, but no longer taking on new participants.
Completed: The trial has finished. Results may not be published yet.
Stopped early: Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled: Cancelled before anyone took part.

Expanded access

Not trials. A few records describe treatments that can be requested outside a study, and these statuses say whether that route is open.

Expanded access: Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused): Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended): Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved: The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Two statuses say something about the record rather than about recruitment. Neither tells you whether anyone can join.

Details not published: The full record has not been published yet, so there is little to show here.
Status unknown: This status has not been confirmed recently, so it may be out of date.

Phase

How far along a treatment is in being tested. Phases describe drug development; plenty of studies aren't organised that way at all.

Early phase 1: The earliest testing in people: a first look at safety, in a very small group.
Phase 1: The first testing in people. Mainly checks safety and dose, usually in a small group.
Phase 2: Tests whether the treatment actually works, and watches for side effects, in a larger group.
Phase 3: Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.
Phase 4: Runs after approval, following long-term safety and how well the treatment works in everyday use.
Phase 1/2: Runs two stages together: safety and dose first, then whether the treatment works.
Phase 2/3: Runs two stages together: whether the treatment works, then large-scale confirmation.
Not a phased trial: Phase numbers describe drug development. The registry uses this when they do not apply, as it does for trials of devices, procedures or behaviour changes, and for observational studies.
Other combinations: Runs more than one stage of testing together.

Kinds of lead sponsor

The registry records what kind of person or organisation the lead sponsor is. It does not record who pays for the study or who carries it out.

A company: The lead sponsor is a pharmaceutical, biotech, or medical-device company.
Other sponsor: The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
A government research agency: The lead sponsor is the US National Institutes of Health.
A government agency: The lead sponsor is a US federal agency other than the NIH.
A government agency: The lead sponsor is a government body.
A research network: The lead sponsor is a research network or cooperative group.
An individual researcher: The lead sponsor is a named person rather than an organisation.

Other terms you'll see

Eligibility criteria: The study team's rules for who may join. Usually split into inclusion criteria, which you must meet, and exclusion criteria, which rule you out. Only the study team can say for certain whether you qualify.
Healthy volunteer: Someone in good general health who takes part in a study. Not simply anyone without the condition being studied: a person living with an unrelated serious illness isn't a healthy volunteer either. And a study that doesn't accept them isn't necessarily open only to people who already have the illness. Prevention and genetic-risk studies often sit in between.
Placebo: A stand-in for the treatment being tested, given so its effect can be told apart from the effect of being treated at all. Often an inactive pill, but it may be a dummy procedure or device, or even an active substance chosen to reproduce the side effects, making the group harder to guess from how someone feels. Not every study uses one.
Randomised: Participants are put into groups by chance rather than by choice, so neither the doctor nor the patient decides who gets what. That makes the groups more likely to be alike at the start, though in a small study chance can still leave real differences between them.
Blinded, or masked: Some of the people involved are not told who is receiving which treatment, so expectations are less likely to colour the results. It isn't foolproof: noticeable side effects can still give the group away. A double-blind study keeps two of those groups unaware; which two depends on the study.
Enrollment: How many people take part. The registry marks the figure as either estimated (the number a study aims to recruit, which can change) or actual, the number who did. A study finishing doesn't turn one into the other; plenty of finished records still carry an estimate.
Primary outcome: The main thing a study measures to answer its central question. Other things measured along the way are secondary outcomes.
NCT ID: The identifier a study is given on ClinicalTrials.gov, the public registry this site draws from. It looks like NCT01234567 and is the surest way to look a study up elsewhere.

These explanations are here to make trial listings readable. They are not medical advice, and they can't tell you whether a particular study is right for you, but a doctor who knows your case can.