Study types and bias—Don’t judge a study by the abstract’s conclusion alone

Why is it important to consider the study design before implementing the findings?

Not all study designs are created equal. Some designs are inherently better at minimizing bias. Bias (usually unintended) is one of the greatest threats to a study’s conclusion. In this issue of EBSJ, we will discuss the strengths and weaknesses of the common study designs that you are most likely to encounter in the literature or consider for your next study.

What is the primary goal of a clinical study?

The goal of most clinical studies is to evaluate a treatment method and to report the most accurate and unbiased effect of the treatment. One important way to help minimize bias is to select the best study design to accomplish your purpose.

There are three frequently used study designs we will discuss today: the randomized controlled trial, the cohort study, and the case series. There are costs and benefits to each that must be weighed. We will also discuss how registry studies fit into this paradigm since there is a movement toward using registries for comparative effectiveness research.

Randomized controlled trials

When comparing two treatments, the comparison groups should be comprised of participants who are similar in all respects, with the exception of the particular treatment(s) that is being studied. The best method to achieve this similarity between groups is that of random assignment.

The randomized controlled trial (RCT) provides the strongest evidence for safety and effectiveness and is considered the gold standard for therapeutic studies.