Glossary ImageGlossary of Terms

Additional definitions of clinical trial terms can be found on the NIH website's glossary.


An ECG is an electrocardiogram, or a graphical recording of the cardiac cycle produced by an electrocardiograph. This is a quick procedure which includes placing sticky electrodes on the skin of the participant's chest, arms, and legs. The participant then lies still for approximately one minute. The procedure usually takes about 5-10 minutes total (the longest part is placing the electrodes). This test is to determine the health of the participant's heart.

Healthy Volunteer

For the purposes of studies at the IDCTU, this refers to individuals 18-45 years old without any significant health problems. The requirements to participate as a healthy volunteer may vary slightly from study to study, but in general healthy volunteers are also light to non-smokers, of a healthy weight, and not pregnant.


The screening visit involves a series of questions (medical history). it may also include a physical exam, blood draw(s), urine sample(s), and other tests specific to the study, such as an ECG or eye exam. The reason for this visit is to determine if a volunteer is eligible to participate in a particular study. The study staff reviews all the data from the screening visit and will inform the participant if they are eligible to participate in the study or not. The participant can decide at any time during this process to decline participation.

Informed Consent

Informed consent is the process of learning the key facts about a clinical trial before deciding whether or not to participate. It is also a continous process throughout the study to provide information for participants. To help someone decide whether or not to participate, the doctors and nurses involved in the trial explain the details of the study. Then the research team provides an informed consent document that includes details about the study, such as its purpose, duration, required procedures, and key contacts. Risks and potential benefits are explained in the informed consent document. The participant then decides whether or not to sign the document and participate in the study. Informed consent is not a contract, and the participant may withdraw from the trial at any time.

Phase 1 Trials

Initial small studies (20-80 participants) to determine the safety, appropriate dosage, and side effects associated with an experimental drug or treatment; may include healthy volunteers or patients with a specific medical condition.

Phase 2 Trials

Moderately sized studies (100-300 participants) to test the effectiveness of an experimental drug or treatment in patients with a particular disease or condition and further evaluate its safety; only performed after successful Phase 1 trials.

Phase 3 Trials

Large studies (1,000-3,000 participants) to compare an experimental drug or treatment to currently available treatments, monitor side effects, confirm its effectiveness, and gather additional information for proper labeling of the drug (if applicable); only performed after successful Phase 1 and 2 trials.


A placebo is an inactive pill, liquid, or powder that has no treatment value. In clinical trials, experimental treatments are often compared with placebos to assess the experimental treatment's effectiveness. In some studies, the participants in one group will receive a placebo instead of an active drug or experimental treatment.

Principal Investigator

This is the head of the clinical trial. Sometimes this position is shared. In the case of the IDCTU, this person is Dr. Robert Salata.