Types of clinical trials in Drug Development process

There are different types of clinical trials.

• Natural history studies provide valuable information about how disease and health progress.
• Prevention trials look for better ways to prevent a disease in people who have never had the disease or to prevent the disease from returning. Better approaches may include medicines, vaccines, or lifestyle changes, among other things.
• Screening trials test the best way to detect certain diseases or health conditions.
• Diagnostic trials determine better tests or procedures for diagnosing a particular disease or condition.
• Treatment trials test new treatments, new combinations of drugs, or new approaches to surgery or radiation therapy.
• Quality of life trials (or supportive care trials) explore and measure ways to improve the comfort and quality of life of people with a chronic illness.

http://www.nih.gov/health/clinicaltrials/basics.htm