What is a Clinical Study?
Clinical research can be divided into clinical studies and clinical trials. A clinical study is any type of clinical research involving patients that involves non-interventional research, such as observational studies.
Another common type of clinical research study is a clinical trial. A clinical trial is a research study designed to test the safety and/or effectiveness of drugs, devices, and other medical interventions. Clinical trials can be divided into three different "phases." (see: What is a Clinical Trial?).
Most commonly a clinical trial involves an intervention with a potential medication or other form of treatment. Often these studies involve control groups in order to better assess the treatment that is being studied. The group receiving the experimental medication is compared to the control group who given an inactive treatment, called a placebo, an inert substance such as a sugar pill that looks like the experimental medication. Whether one is assigned to the active treatment group or to the control group is determined randomly (by a "flip of the coin"). The administering doctor or nurse will not know which treatment you are on (see informed consent language). Nor will you be informed at the time of the study participation to which group you have been assigned. This is called the Double Blind. This is done to prevent bias in the assessment of the effects of the experimental medication.
At the end of the study, the effects of the experimental medication and the placebo are compared to see if the medication made a significant difference. Surprisingly, placebos often have a modest beneficial effect. So, by designing the clinical trial in this way, researchers can determine the true effect of the medication. A clinical trial can also involve a trial of a device or a surgical procedure.
An observational study is a type of clinical study. In this type of study a subject at risk for the disease or a patient with the disease is followed for several years to better understand the disease natural history, how it progresses over time. This information is important in understanding the disease better, and is thus critical for designing better clinical trials.
A cross-sectional study is a clinical research study where a large number of patients at different stages of the illness are evaluated. Both observational and cross-sectional studies are needed for biomarker studies; these are clinical studies that look for ways to understand the changes associated with the disease and its progression. Most commonly these are blood or urine tests, cognitive assessments or brain imaging, but biomarker studies can involve tests of spinal fluid, smell tests, biopsy of skin or muscle, tests such an EKG or EEG (brain waves), or even tests of coordination or behavior. Clinical trials frequently use biomarkers to determine whether a drug has indeed the expected response in the patient's body. The hope for Huntington's disease is that a biomarker (or set of biomarkers) could be found that would tell if a drug is working within a few weeks or months, rather than the several years it might take for a physician to determine an effect based on visits to the clinic.