About Clinical Trials

What is a Clinical Trial

Clinical trials are the path over which all new medical therapies must travel to become accepted practice—and the path is a long one. For patients, clinical trials can typically last for a few weeks or months. For scientists, they can continue on for years before a new therapy may see the light of day.

There are different types of clinical trials: treatment, prevention, diagnostic, screening, and quality of life trials—and the trials are conducted in progressive phases (I-IV). Once a clinical trial reaches the end of the path–proving its potential worth as a medical therapy–the Food and Drug Administration (FDA), a government agency, must officially approve the therapy for medical consumers.

For patients, participation in a clinical trial is voluntary. Common reasons for joining a clinical trial include: playing a more active role in your own health care; gaining access to innovative treatments before they become widely available; and helping others by contributing to advancements in medical research.

How Do Clinical Trials Work?

To ensure that no one can influence the results of a study, clinical trials employ a range of specialized testing mechanisms intended to prevent bias and provide reliable results:

  • Prospective Trials—Patients are identified and then followed over time.
  • Randomized Trials—Patients are grouped by chance into (typically) a treatment group and a control group (also called a placebo group). A control group receives either the current standard treatment or a placebo-an inactive pill or liquid. The results of the control group are then compared with those of the treatment group.
  • Cross-over Trials—Patients receive both the treatment and the placebo at different times, with careful monitoring of their responses to both approaches.
  • Double-blinded Trials—Neither the patient nor the researcher knows if the patient is receiving the treatment or the placebo.

In addition, some clinical trials are called open label studies, because both the patient and the researcher know that the patient is receiving the treatment and not the placebo.

By federal regulation, every clinical trial in the United States must be approved and monitored by an Institutional Review Board (IRB), an independent committee of physicians, statisticians, community advocates, and others. The IRB is charged with ensuring that all clinical trials within a given medical institution are ethical and that the rights of the participants in those trials are protected.

Clinical trials retain very specific participation guidelines. Establishing and maintaining these guidelines is a critical part of producing meaningful and reliable results. The factors that allow someone to participate in a clinical trial are called "inclusion criteria," while those that disallow someone are called "exclusion criteria." Typical criteria include age, gender, the type and stage of a disease, previous treatment history, and other medical conditions.

What are the Phases of Clinical Trials?

Clinical trials are conducted in phases. Each phase of a trial has a different purpose and helps scientists to answer specific questions.

While small, early phase trials may be conducted by individuals or small groups of physicians, larger trials are typically conducted by hospitals, pharmaceutical companies, or device manufacturers. If a therapy successfully passes through Phase III trials, the FDA may approve it to be marketed to the public.

Phase Definition

Phase I Trials

Researchers test a new drug or treatment in a small group of people (20-80) for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.

Phase II Trials

The study drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety.


Phase III Trials

The study drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug or treatment to be used safely.

Phase IV Trials

Post-marketing studies delineate additional information including the drug's risks, benefits, and optimal use.

What are the Different Types of Clinical Trials?

  • 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 a given disease in people who have never had that disease or to prevent a disease from returning. Preventative approaches include medicines, vitamins, vaccines, minerals, and 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.