Non Randomized Clinical Trial
- Participants are assigned to treatment or control groups using criteria other than randomization (e.g., medical history or willingness to participate).
- Common forms include prospective and retrospective studies, case-control studies, and observational studies.
- Faster and less expensive than randomized trials but more susceptible to bias and confounding and may not be representative of the general population.
Definition
Section titled “Definition”A non-randomized clinical trial is a research study conducted to evaluate the effectiveness and safety of a medical treatment or intervention that does not use random assignment. Instead of randomization, participants are assigned to the treatment or control group based on certain criteria, such as their medical history or their willingness to participate in the study.
Explanation
Section titled “Explanation”Non-randomized clinical trials encompass several study designs — including prospective and retrospective studies, case-control studies, and observational studies — which differ in characteristics and research questions but share the feature that participants are not randomly assigned to receive a treatment. These studies collect and analyze data from groups of participants whose group membership is determined by predefined criteria rather than by chance.
Advantages noted for non-randomized trials include the ability to conduct studies more quickly and at lower cost, and the feasibility of studying rare or hard-to-treat conditions when randomized trials are impractical. Disadvantages include greater susceptibility to bias and confounding, increased difficulty in interpreting results regarding treatment effectiveness and safety, and potential lack of representativeness because participants are selected based on criteria rather than random sampling.
Examples
Section titled “Examples”Prospective Study
Section titled “Prospective Study”A prospective study enrolls participants at the start of the study and follows them over time to observe the effects of a treatment or intervention. For example, a prospective study might enroll a group of patients with a specific medical condition and follow them for several months to evaluate the effectiveness of a new drug or treatment. The goal is to identify trends or patterns in the data that show how the treatment affects participants over time.
Case-Control Study
Section titled “Case-Control Study”A case-control study compares two groups of people: those who have a specific medical condition (the cases) and those who do not (the controls). The goal is to identify factors that may be associated with development of the condition, such as genetic or environmental factors. For example, a case-control study might compare a group of patients with cancer to a group of healthy individuals to identify potential risk factors for the development of cancer.
Use cases
Section titled “Use cases”- Conducting studies more quickly and at lower cost than randomized trials.
- Studying rare or hard-to-treat conditions where assembling randomized cohorts is difficult.
- Complementing randomized trials when a combination of evidence types is needed to understand treatment effects.
Notes or pitfalls
Section titled “Notes or pitfalls”- More prone to bias and confounding because group assignment is not random.
- Greater difficulty in accurately interpreting results and drawing causal conclusions about effectiveness and safety.
- May not be representative of the general population due to participant selection based on specific criteria.
Related terms
Section titled “Related terms”- Randomized clinical trial
- Prospective study
- Retrospective study
- Case-control study
- Observational study