What is a Clinical Study?

There are two main types of clinical studies: clinical trials and observational studies. Both involve using human participants to conduct research intended to enhance medical knowledge.

Clinical Trials

In a clinical trial, participants receive specific interventions according to the research protocol. These interventions may be medical products, or changes to participants' behavior, such as activity or diet. Clinical trials may compare a new medical approach to a standard one that is already available, or to a placebo that contains no active ingredients. Some clinical trials compare interventions that are already commercially available. When a new product or approach is being studied, investigators try to determine the safety and effectiveness of the intervention by monitoring certain outcomes in the participants. Prior to the trial, it is typically not known whether the intervention will be helpful, harmful, or no different than available alternatives.

Clinical trials used in drug development are often conducted in phases to ensure a thorough investigation. There are four different phases:

1. Phase I trials are conducted by testing an experimental drug or treatment in a small group of people to evaluate its safety, determine a safe dose range, and identify any side effects. This is the first time the experimental condition is tested on human volunteers.
2. In phase II trials researchers test the experimental drug or treatment on a larger group of people for further evaluation of safety and efficacy. 
3. Phase III studies are conducted with a large group of people to confirm the efficacy and monitor side effects of the drug or experimental treatment. It is also compared to other commonly-used treatments at this time.
4. Phase IV trials delineate further information including risks and benefits associated with the drug or treatment, in addition to optimal use.
   
   

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 or procedures as part of their routine medical care, but they 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.

Who Conducts Clinical Studies?

Every clinical study is led by a principal investigator (PI), who is often a medical doctor. Clinical studies also have a research team that may include doctors, nurses, social workers, and other health care professionals.

Clinical studies can be sponsored, or funded, by pharmaceutical companies, academic medical centers, voluntary groups, and other organizations, in addition to Federal agencies such as the National Institutes of Health, the U.S. Department of Defense, and the U.S. Department of Veterans Affairs. Doctors, other health care providers, and other individuals can also sponsor clinical research.

Where Are Clinical Studies Conducted?

Clinical studies can take place in many locations, including hospitals, universities, doctors' offices, and community clinics. The location depends on who is conducting the study.

How Long Do Clinical Studies Last?

The duration of a clinical study varies greatly depending on the research they are conducting.

Common Reasons For Conducting Clinical Studies

Clinical studies are designed to enhance medical knowledge related to the treatment, diagnosis, and prevention of diseases or conditions

• To evaluate an intervention such as a drug, medical device, or approach to surgery
• To search for ways to prevent the occurrence of a medical condition, include medicines, vaccines, or lifestyle changes, among other approaches
• To evaluate ways to identify or diagnose a particular disease or condition
• Examining methods for identifying a condition or the risk factors for that condition

Participating in Clinical Studies

A clinical study is conducted according to a research plan known as the protocol, designed to answer specific research questions and safeguard the health of participants. It contains the following information:

• The reason(s) for conducting the study
• Criteria for volunteer participation
• The number of participants needed
• The schedule of tests, procedures, and/or drugs
• The duration of the study
• The information that needs to be gathered about the participants

Who Can Participate in a Clinical Study?

Volunteers cannot participate in any clinical study they choose. There are standards called eligibility criteria and are listed in the protocol. While some research studies seek participants who have the illnesses or conditions that will be studied, other studies are looking for healthy participants. The factors that allow someone to participate in a clinical study are called inclusion criteria, and the factors that disqualify someone from participation are called exclusion criteria. Inclusion and exclusion criteria may be based on age, gender, previous treatment history, and other medical conditions.