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Understanding Research - Types & Phases of Clinical Trials

What are the different types and phases of clinical trials?

Clinical trials are prospective. They are research studies conducted with people who volunteer to participate. These studies are done to find out whether promising approaches to heart disease prevention, diagnosis, and treatment are safe and effective. They often test whether a suggested relationship uncovered in an observational study or retrospective study is in fact true. Clinical trials help establish a causal link between a treatment and a specific medical outcome, such as whether taking hormone replacement therapy will lead to fewer heart attacks.
There are three major types of clinical trials:

  • Treatment trials test treatments, such as medications, surgical procedures, or combinations of the two.
  • Prevention trials test whether specific medicines, vitamins, minerals, diets, or lifestyle lower the risk of developing heart disease. These trials look for the best way to prevent heart disease in people who have never had it or to prevent heart disease from becoming worse in people who already have it.
  • Diagnostic trials test the best way to diagnose heart disease using different techniques. These include imaging tests, such as angiograms, echocardiograms, ultrasound, or laboratory tests that look at a woman’s blood or urine. An example would be taking a blood test in order to look at whether an increased level of C-reactive protein indicates the presence of heart disease.

Before a new drug or treatment can be launched, it has to be tested to show that it’s safe and effective. These trials involve a series of steps, known as phases. They are usually classified into one of four phases. Only the treatments that perform well in the early phases move forward to Phase III trials.

  • Phase I trials: These are the first studies to look at how a new intervention works in people. They mainly test safety; for example, with a drug, they determine what dose is safe, and whether it has any toxic or negative effects. These trials generally enroll only a small number of participants, sometimes as few as a dozen.
  • Phase II trials: These trials continue to test the safety of treatments that had good results in a Phase I trial. Phase II trials evaluate how effective the treatment is — in other words, how well it works.
  • Phase III trials: These studies are carefully designed in order to show that the drug works as intended, has a low incidence of toxicity, and is safe for patients to take. In these trials, the new intervention is usually compared with the current standard of care, for example, the drug most often prescribed for high blood pressure. These trials usually enroll large numbers of people and may be conducted at doctors’ offices, clinics, and cardiac care units across the nation. Because they build on reliable findings from earlier trials, Phase III trials are considered to be the ultimate test of a new intervention, and are the basis for approval by the Food and Drug Administration (FDA).
  • Phase IV trials: This phase of testing occurs after the drug has already received FDA approval for use and is being prescribed to patients. These trials continue to monitor the use of the drug, along with any side-effects that occur with long-term usage.

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