Clinical Trials

The Basics of Clinical Studies

A clinical study, synonymous to clinical research, involves research using human volunteers (also called participants) and is intended to add to medical knowledge by answering specific health questions. Carefully conducted clinical trials are the fastest and safest way to find treatments and improve health on both a micro-individual level and macro-community level.

There are two main types of clinical studies: clinical trials (also called interventional studies) and observational studies. Interventional trials determine whether experimental methods, which involve new ways of using existing therapies, or investigational treatments are safe and effective under controlled experimental conditions. Observational trials address health issues in large groups of people or populations in natural settings.

Clinical Trials

In a clinical trial, participants receive specific interventions according to the research plan or protocol created by the investigators. These interventions may be medical products, such as drugs or devices; procedures; or changes to participants' behavior, such as diet. Clinical trials may compare a new medical approach to a standard one that is already available, to a placebo that contains no active ingredients, or to no intervention. Some clinical trials compare interventions that are already available to each other. When a new product or approach is being studied, it is not always known how the outcomes will compare to the available alternatives (including no intervention). The investigators try to determine the safety and efficacy of the intervention by measuring certain outcomes in the participants. For example, investigators may give a drug or treatment to participants who have high blood pressure to see whether their blood pressure decreases.

Clinical trials used in drug development are sometimes described by phase. These phases are defined by the Food and Drug Administration (FDA).

Observational Studies

In an observational study, investigators assess health outcomes in groups of participants according to a research plan or protocol. Participants may receive interventions (which can include medical products such as drugs or devices) or procedures as part of their routine medical care, but participants are not assigned to specific interventions by the investigator (as in a clinical trial). For example, investigators may observe a group of older adults to learn more about the effects of different lifestyles on cardiac health.

Different types of clinical Trials And Their Purpose:

In general, clinical studies are designed to add to medical knowledge related to the treatment, diagnosis, and prevention of diseases or conditions. Some common types of trials and reasons for conducting clinical studies include:


  • Treatment trials test new treatments, new combinations of drugs, or new approaches to surgery or radiation therapy.

  • Prevention trials look for better ways to prevent disease in people who have never had the disease or to prevent a disease from returning. These approaches may include medicines, vitamins, vaccines, minerals, or lifestyle changes.

  • Diagnostic trials are conducted to find better tests or procedures for diagnosing a particular disease or condition.

  • Screening trials test the best way to detect certain diseases or health conditions.

  • Quality of Life trials (or Supportive Care trials) explore ways to improve comfort and the quality of life for individuals with a chronic illness.


The above information is provided by the center for information and study on clinical research participation (CISCRP), a non-profit organization dedicated to educating the public and patients in the clinical research process ciscrp.org/. Information also provided by clinicaltrials.gov, a service of the National Institute of Health. Additional resources for information and frequently asked questions about clinical trials for patients and their families can be found at: