Any of the treatment groups in a clinical trial.


Baseline information is gathered at the beginning of a study from which variations found in the study are measured. Baseline can also be described as a value or quantity with which an unknown ix compared when measured or assessed. Safety and efficacy of a treatment are often determined by monitoring changes from the baseline values.

Blind, Blinded or Blinding

A clinical trial is “blinded” if the participants are unaware on whether they are in the experimental or control arm of the study. Blinding may also be extended to the investigators so that their patient observations are less likely to be biased by their awareness of the treatment the patient is receiving.


Pertaining to or founded on observation and treatment of human participants or patients, as distinguished from theoretical or basic science.

Clinical Investigator

A medical researcher in charge of carrying out a clinical trial’s protocol.

Clinical Trial

Clinical trials, also known as clinical studies, test potential treatments in human volunteers or patients. A treatment could be a drug, medical device, or biologic, such as a vaccine, blood product, or gene therapy. Potential treatments must first be studied in laboratory models or animals to determine its safety before they can be tried in people. Treatments having acceptable safety profiles for the disease or condition and showing the most promise are then moved into clinical trials.

Control Group

A control is the standard by which experimental observations are evaluated. In many clinical trials, one group of patients will be given an experimental drug or treatment, while the control group is given either a standard treatment for the disease or condition or a placebo.

Dose-Ranging Study

A clinical trial in which two or more doses of an agent (such as a drug) are tested against each other to determine which dose works best and is least harmful.

Double-Blind Study

A clinical trial design in which neither the participating individuals nor the study staff knows which participants are receiving the experimental drug and which are receiving a placebo or another therapy.


The ability of a drug or treatment to produce a beneficial result.

Eligibility Criteria

Summary criteria for participation selection; includes inclusion and exclusion criteria.


Based on observation or experience, not experimental data.


Overall outcome that the protocol is designed to evaluate.

Exclusion/Inclusion Criteria

The medical or social standards determining whether a person may or may not be allowed to enter a clinical trial. These criteria are based on such factors as age, gender, pregnancy status, the type and stage of the disease, previous treatment history, and other medical conditions.

In Vivo

Testing or action inside an organism, such as a human subject or patient.

In Vitro

Testing or action outside an organism (i.e. inside a test tube or culture dish)

Multicenter Trial

A clinical trial conducted according to a single protocol but at more than one site, and therefore, carried out by more than one investigator.

Open-Label Trial

A clinical trial in which doctors and participants know which treatment is being administered.

Pivotal Study

A study, usually Phase III, which presents the data used by regulatory agencies to decide whether to approve a drug.


A placebo is an inactive pill, liquid or powder, that has no treatment value. In clinical trials, a placebo is administered instead of an active drug or experimental treatment to assess the experimental treatment’s effectiveness.


A protocol is the study plan on which a clinical trial is based. Each trial is carefully designed to safeguard the health of the participants as well as answer specific research questions. A protocol describes what types of people may participate in the trial, the schedule of tests, procedures, medications, dosages, and the length of the study.


A method based on chance by which study participants are assigned to different treatment groups.

Standards of Care

Treatment regimen or management based on state of the art medical care.