What's clinical trials?
For the purposes of registration, a clinical trial is any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcomes. Clinical trials may also be referred to as interventional trials. Interventions include but are not restricted to drugs, cells and other biological products, surgical procedures, radiologic procedures, devices, behavioural treatments, process-of-care changes, preventive care, etc. This definition includes Phase I to Phase IV trials.
Why do we need clinical trials[4]?
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Clinical trials are essential to the development of new interventions. For example, without clinical trials, we cannot properly determine whether new medicines developed in the laboratory or by using animal models are effective or safe, or whether a diagnostic test works properly in a clinical setting.
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Clinical trials also permit testing and monitoring of the effect of an intervention on a large number of people to ensure that any improvement as a result of the intervention occurs for many people and is not just a random effect for a one person.
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Clinical trials can also help to improve health care services by raising standards of treatment. Doctors and hospital staff involved in clinical trials are continually trained to provide best practice patient care. Australian clinical trials are recognised internationally for including very high quality patient care.
Clinical trials classfication
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Primary research has been categorized in different ways. Common categorization schema include temporal nature of the study design (retrospective or prospective), usability of the study results (basic or applied), investigative purpose (descriptive or analytical), purpose (prevention, diagnosis or treatment), or role of the investigator (observational or interventional)[1].
Classified by Purpose
There are several types of cancer clinical trials, including treatment trials, prevention trials, screening trials, quality of life trials, and natural history studies.
- Treatment trials
- Prevention trials
- Screening trials
- Quality of life trials
- Natural History Studies
Classified by Role of the investigator
Within primary research there are observational studies and interventional studies.
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Observational studies, also called epidemiological studies, are those where the investigator is not acting upon study participants, but instead observing natural relationships between factors and outcomes.
Observational trials look at certain factors or outcomes (e.g., disease progression) over time. Other studies examine what risk factors are associated with the development of a condition. Diagnostic studies are classified as observational studies, but are a unique category and will be discussed independently. -
Interventional studies, also called experimental studies, are those where the researcher intercedes as part of the study design.
Interventional trials test new drugs or other types of therapies, or determine whether already approved therapies can be used in new ways.
Classified by Time course
Study designs may be classified by the role that time plays in the data collection, either retrospective or prospective.
Retrospective studies are those where data are collected from the past, either through records created at that time or by asking participants to remember their exposures or outcomes. Such a study might, for example, analyze medical records or stored blood samples. Retrospective studies cannot demonstrate temporality as easily and are more prone to different biases, particularly recall bias.
Prospective studies follow participants forward through time, collecting data in the process.Typically, a study cohort is selected and followed for a predefined period, sometimes several years. Prospective studies are less prone to some types of bias and can more easily demonstrate that the exposure preceded the disease, thereby more strongly suggesting causation.
Several characteristics influence the usefulness of a trial and the credibility of its results. As noted above, the “gold standard” for clinical trials is the prospective, double-blind, randomized, controlled trial with clinically meaningful endpoints. Often, however, one or more of these criteria cannot be fulfilled.
参考资料
- Thiese MS. Observational and interventional study design types; an overview. Biochem Med (Zagreb). 2014;24(2):199-210. doi:10.11613/BM.2014.022.
- Ranganathan P, Aggarwal R. Study designs: Part 1 - An overview and classification. Perspect Clin Res. 2018 Oct-Dec;9(4):184-186.
- https://www.cancer.gov/about-cancer/treatment/clinical-trials/what-are-trials/types
- https://www.australianclinicaltrials.gov.au/what-clinical-trial#:~:text=The%20World%20Health%20Organization%20%28WHO%29%20definition%20for%20a,trial%20interventions%20include%20but%20are%20not%20restricted%20to%3A
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