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Difficulty: MediumStudy Design

Investigators at an academic medical center are designing a clinical study to evaluate a novel sublingual medication for the management of chronic, stable angina. The primary endpoint is the reduction in weekly angina episodes over a 4-week observation period. The research team is concerned that baseline differences in coronary anatomy, physical conditioning, and lifestyle habits will introduce significant between-subject variability, potentially masking the drug's true effect. To maximize statistical power and completely eliminate this between-subject confounding, the investigators require a design where each participant serves as their own control. Which of the following is the most appropriate study design for this investigation?

  1. Crossover randomized trialAnswer
  2. B
    Parallel-group randomized trial
  3. C
    Factorial randomized trial
  4. D
    Stepped-wedge cluster trial
  5. E
    Nested case-control study

Answer

Crossover randomized trial
The correct answer is the crossover randomized trial. In this study design, each participant is randomly assigned to a sequence of treatments. For example, a patient may receive the active drug for 4 weeks, undergo a washout period to allow the drug to leave their system, and then receive the placebo for 4 weeks. Because the exact same individual provides data for both the active and control phases, differences related to genetics, anatomy, and lifestyle (between-subject variability) are perfectly controlled. This design is highly efficient and requires a smaller sample size, but it is strictly limited to chronic, stable conditions (like stable angina or asthma) where the underlying baseline disease does not rapidly progress or cure itself between periods.

Step-by-Step Solution

1
Identify the primary objective and constraints of the investigators.
They want to evaluate a new treatment while completely eliminating between-subject variability by having patients serve as their own controls.
Understanding the methodological requirement (self-control) points directly to specific experimental designs.
2
Evaluate the clinical context of the condition being studied.
The condition is chronic, stable angina, which is a predictable, ongoing disease rather than an acute, curable illness.
Certain study designs require a return to baseline (washout). This is only possible in chronic, stable conditions.
3
Match the methodological requirement to the correct study design.
A crossover trial gives patients Treatment A, followed by a washout period, followed by Treatment B. This sequence ensures every participant acts as their own control.
This is the classic and optimal design for maximizing power and eliminating interpersonal confounding in stable chronic diseases.

Key Concept

Crossover study design
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Topics

Study Design

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