A prospective study of an intervention via a clinical research STUDY or CLINICAL PHARMACOLOGY TRIAL. In this type of trial neither the researchers nor the participants know who receives what agent or treatment, and participants are randomly assigned to a group without any qualifying factors. A pharmacist may prepare medication dosages (typically in forms that appear identical), which are dispensed to, or a clinician administers to, participants. Cross-referenced records are created to document all procedures; researchers compile the records when the trial is completed. The randomized double-blind study is considered to be one of the most objective models for conducting research because it prevents bias and expectations of either participants or researchers from influencing observations and outcomes or findings as neither knows which participants are in which group until the study is finished.
Typically a randomized double-blind study compares one agent or treatment with another, and participants in each group receive some form of treatment. There may be two or more groups, depending on the topic researchers are investigating. This is a common method for evaluating an investigational new drug (ind), for example, or for determining which of two or more commonly used treatments is more effective.
When there is also a group that does not receive any treatment, the trial is also called a controlled trial those who do not receive treatment are the control group, a representation of a general population against which researchers can compare the outcome or findings of the agent or treatment being evaluated. A placebo-controlled study uses a control group that receives a placebo (inert substance or agent) instead of medication. Control groups are not used as commonly in trials involving treatments for Parkinson’s disease because people with Parkinson’s must have treatment and there usually is little value in comparisons to people who do not have Parkinson’s. Studies involving lifestyle factors or nutritional supplements may be among the exceptions.
Randomized double-blind studies generally produce the most reliable results; findings are compared against statistical standards for perspective. A randomized double-blind study is not always possible, as when a treatment is invasive (surgery). Anyone considering participation in any clinical research trial should make sure to understand fully what agent or treatment is being evaluated, what the expected results are, what the potential risks are, and what signs and symptoms are indications of possible adverse reactions.