National EMSC Data Analysis Resource Center
Prospective study design is the best design for establishing relationships between your outcome of interest and exposure variables. The primary feature of prospective designs is the outcome has not occurred at the time the study is initiated, and information is collected over time to assess relationships with the outcome.
In a prospective cohort study, subjects are identified based on exposure status prior to the development of the disease or condition of interest, and the outcome is measured over time. In this type of study, the investigator can establish a temporal relationship between an exposure and an outcome, or follow the natural development of a condition over time.
Randomized controlled trials (RCTs) are considered the gold-standard of study design. They can provide evidence for causal relationships and support changes in clinical practice. In an RCT, subjects are randomly assigned to receive the intervention or control treatment, and outcomes are evaluated after the intervention period. The control group is the group which receives the standard of care (or a placebo).
It is very important that the investigator and subjects are blinded to which treatment the subjects receive. This is called a double-blind study. Conducting a double-blind study helps to reduce any potential bias in the results of the study.