A clinical study (sometimes called a clinical research study, trial, or protocol) is a way to determine appropriate dosing of new medications and use of medical devices as well as ensure they are safe and effective. Medications being researched for safety and effectiveness are known as investigational drugs or study drugs. Clinical trials involve the testing of these new investigational drugs or medical devices in phases that allow doctors and researchers to obtain reliable information about the drug or device and, at the same time, protects the patient.

Clinical trials or studies can also be described based on their plan of action. Some examples include:

• Treatment trials – Treatment trials test new treatments and might include new medications, therapies, devices or approaches to surgery.
• Diagnostic studies – Diagnostic studies are conducted to find new tests or procedures for diagnosing certain diseases or conditions.
• Screening studies – Screening studies focus on the best ways to detect certain diseases or conditions.
• Quality of life trials – Quality of life trials looks at how different factors, including treatment, affect the quality of life for individuals living with specific diseases or conditions being studied.
• Prevention studies – Prevention studies test ways to decrease or prevent diseases or conditions from developing or getting worse. These studies may include medicines, vitamins, or other lifestyle modifications.