In a clinical trial, patient outcomes are measured before and after receiving some type of medical intervention. Participants receive the intervention(s) 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 usually known whether it will be helpful, harmful, or no different than 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 Therapeutic Product Directorate (Health-Canada), the US-Food & Drug Administration (FDA) and the European Medicines Agency (EMA).

Some people who are not eligible to participate in a clinical trial may be able to get experimental drugs or devices outside of a clinical trial through expanded access. See more information on expanded access from Health Canada.

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

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.

The length of a clinical study varies, depending on what is being studied. Participants are told how long the study will last before they enroll.

Clinical studies have standards outlining who can participate. These standards are called eligibility criteria and are listed in the protocol. Some research studies seek participants who have the illnesses or conditions that will be studied; other studies are looking for healthy participants, and some studies are limited to a predetermined group of people who are asked by researchers to enroll.

Eligibility. The factors that allow someone to participate in a clinical study are called inclusion criteria. The factors that disqualify someone from participating are called exclusion criteria. Inclusion and exclusion criteria are based on characteristics such as age, gender, the type and stage of a disease, previous treatment history, and other medical conditions.

Informed consent is a process used by researchers to provide potential and enrolled participants with information about a clinical study. This information helps people decide whether they want to enroll or continue to participate in the study. The informed consent process is intended to protect participants and should provide enough information for a person to understand the risks, potential benefits, and alternatives to participating in the study. In addition to the informed consent document, the process may involve recruitment materials, verbal instructions, question-and-answer sessions, and activities to measure participant understanding. In general, a person must sign an informed consent document before joining a study to show that he or she understands all of the information about the risks, potential benefits, and alternatives to participating in the study. Signing the document and providing consent is not a contract. Participants may withdraw from a study at any time, even if the study is not over. See the section below “Questions to Ask” for questions to ask a health care provider or researcher about participating in a clinical study.

In Canada, all research involving human participants, their data, or their biological material requires approval by a Research Ethics Board (REB). In the United States, this body is called an Institutional Review Board (IRB). Some, but not all, clinical research also requires authorization by Health Canada. A REB is made up of doctors, researchers, and members of the community. Its role is to make sure that the study is ethical and that the rights and welfare of participants are protected. This includes assessing and minimizing research risks, weighing them against potential benefits, and reviewing the informed consent document, among other responsibilities.

In addition to REB oversight, certain clinical studies may also be subject to monitoring by a data monitoring committee, also known as a data safety and monitoring board (DSMB).

Typically, participants continue to see their usual health care providers while enrolled in a clinical study. While most clinical studies provide participants with medical products or interventions related to the illness or condition being studied, they do not provide extended or complete health care. By having his or her usual health care provider work with the research team, a participant can make sure that the study protocol will not conflict with other medications or treatments that he or she receives.

Participating in a clinical study contributes to medical knowledge. The results of these studies can make a difference in the care of future patients by providing information about the benefits and risks of therapeutic, preventative, or diagnostic products or interventions.
Clinical trials provide the basis for the development and marketing of new drugs, biological products, and medical devices. Some trials may provide participants with the prospect of receiving direct medical benefits, while others do not. Most trials involve some risk of harm or injury to the participant, although it may not be greater than the risks related to routine medical care or disease progression (One responsibility of the REB is to determine if the risks of participation have been minimized and are reasonable in relation to anticipated benefits). Many trials require participants to undergo additional procedures, tests, and assessments based on the study protocol. These requirements will be described in the informed consent document. A potential participant should also discuss these issues with members of the research team and with his or her usual health care provider.