Participating in Clinical Trials
About Clinical Trials
A Research Study With Human Subjects
A clinical trial is a research study that involves human subjects. The purpose of a clinical trial is to find out if an experimental drug, therapy, medical device, lifestyle change, or test will help treat, find, or prevent a disease. A clinical trial may also compare experimental treatments or tests to those already available in order to determine which one is safer or more effective.
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The five main types of clinical trials are treatment, screening, diagnostic, prevention, and quality of life trials.
In treatment trials, researchers may
- gather information about experimental treatments, their risks, and how well they work
- compare existing therapies to decide which one, or a combination of them, is the best treatment for a disease
- evaluate treatment methods such as surgical techniques, psychiatric therapy, or radiotherapy.
Scientists usually do years of experiments in the laboratory and in animals before they even consider testing an experimental treatment in people. Most of this early research occurs at universities and medical centers across the country. The National Institutes of Health funds much of this basic research.
In screening trials, researchers study ways of finding a disease before symptoms occur. These methods, often called screening tests, can include
- imaging tests that produce pictures of what is inside the body
- laboratory tests that check samples of blood, urine, or other body tissues
- genetic tests that look for genes linked to some types of disease.
In diagnostic trials, researchers evaluate new tests that could identify a disease in its early stages. Usually, trial participants must show signs of the disease or condition before they can join this type of trial.
In prevention trials, researchers study ways to reduce the risk of getting a disease or a specific medical problem. These trials find out if
- lifestyle changes, such as exercising more, getting more sleep, keeping mentally active, or eating nutritious foods, can prevent a problem
- taking certain medicines, or vitamins, or getting vaccines will prevent a disease in people who have never had the disease or prevent a disease from returning.
Quality of Life Trials
In quality of life trials, researchers look for ways to make life better for people living with a life threatening disease or chronic health problem. For example, they may study the role of caregivers, support groups, and various types of social interventions.
Three or Four Phases
A clinical trial usually includes three phases. In some cases, four phases may be required.
- A Phase I trial tests an experimental treatment on a small group of often healthy people (20 to 80), to judge its safety and side effects, and to find the correct drug dosage.
- A Phase II trial is similar to a Phase I trial but uses more people (100 to 300) to find out if the experimental treatment is effective and safe. This phase can last several years.
- A Phase III trial is usually a large study with several hundred or more participants (1,000 to 3,000). This phase compares the experimental drug or procedure to a placebo or standard treatment, to make sure it is safe and works well. Some side effects that didn't show up in Phase II may show up in a Phase III trial because many more people are tested. If the U.S. Food and Drug Administration agrees that the trial results are positive, they will approve the experimental drug or device.
- A Phase IV trial for drugs or devices takes place after the U.S. Food and Drug Administration approves their use. A device or drug's effectiveness and safety are monitored in large, diverse populations. Sometimes the side effects of a drug may not become clear until more people have taken it over a longer period of time.