Rapid Research Review: More Study Types

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More Study Types

Case Series

This is used when the objective is to describe and find patterns related to a particular disease/problem. Case series are useful for observing predictive signs, symptoms, and test results. In addition, they help create definitions for medical conditions, promote clinical education/research, and establish safety profiles.

Advantages: useful for rare diseases; can lead to clinical trials.

Disadvantages: no data for true analysis; strong publication bias favors positive results.

Case-Control Study

This is generally an observational, retrospective study of diseased subjects to determine possible exposure risks. One group with a condition/disease, deemed the “case” group, is compared to the “control” group that is similar but does not have the particular disease of interest.

Advantages: Useful for rare diseases, disease with long latency between exposure and onset of illness, and when population is dynamic and difficult to follow over time; convenient to study multiple exposures; relatively low cost

Disadvantages: Many confounding factors; high likelihood recall and selection bias.

Randomized Controlled Trial

A prospective study in which patients with a particular disease are randomly allocated into either a treatment (intervention) or a control (placebo) group.

Advantages: Unbiased distribution of confounding factors; can statistically analyze results

Disadvantages: Ethical issues, time, cost.

Crossover Study

In this type of study there are two or more treatments
applied sequentially on each participant. The participant is
first randomized to treatment 1 and then crossed over to treatment 2.

Advantages: All participants serve as a control so fewer participants are required; all participants receive the treatment; blinding can be maintained; statistical tests can be applied.

Disadvantages: Carry over effect in which action of treatment 2 is impacted by treatment 1.

Clinical Trial

This is an experimental study that compares therapeutic benefits of two or more treatments against a placebo. The quality of a study is thought to be best when the study is randomized, controlled and double-blinded.

ll participants serve as a control so fewer participants are required; all participants receive the treatment; blinding can be maintained; statistical tests can be applied.

  • Phase I: Small number of healthy volunteers to assess safety, toxicity, and pharmacokinetics.
  • Phase II: Small number of patients with the disease of interest to assess the treatment efficiency, optimal dosing, and adverse effects.
  • Phase III: Large number of patients randomly assigned either to the treatment being investigated or to the best available therapy or placebo. Often this is to compare the investigated treatment to the standard of care.
  • Phase IV: Post-marketing surveillance after the drug has been approved to detect rare and/or long-term adverse effects.

Le’Shann Scott, MD
Olga Kovalerchik, MD
EMRA Research Committee

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