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Question

Difficulty: MediumStudy Design

A multidisciplinary task force at a tertiary care hospital is developing a study protocol to investigate prophylactic interventions for postoperative delirium in patients over 65 years of age undergoing major orthopedic surgery. The research team plans to evaluate two separate interventions: a single dose of intravenous haloperidol administered immediately post-surgery, and a standardized non-pharmacologic care bundle focused on sleep hygiene and early mobilization.

The investigators specifically aim to assess the independent effect of the haloperidol, the independent effect of the care bundle, and whether the simultaneous use of both interventions provides a synergistic benefit that exceeds the additive effects of each alone. Furthermore, they wish to answer all three clinical questions using the most statistically efficient patient sample size possible.

Which of the following research designs is most appropriate for this investigation?

  1. Factorial designAnswer
  2. B
    Parallel-group, three-arm design
  3. C
    Crossover design
  4. D
    Cluster-randomized design
  5. E
    Non-inferiority design

Answer

Factorial design
The correct answer is a factorial design. In this specific scenario, a 2x2 factorial design would randomize individual patients into one of four distinct groups: haloperidol only, care bundle only, both interventions simultaneously, and standard care (neither intervention). This design is highly statistically efficient because it utilizes the entire study population to assess the main effect of each intervention. For instance, the main effect of haloperidol is evaluated by comparing all patients who received it (the haloperidol-only group plus the combination group) against all patients who did not receive it. Most importantly, the factorial design is specifically structured to allow for the statistical evaluation of interaction (such as synergy or antagonism) between the two interventions, fulfilling all of the investigators' objectives.

Step-by-Step Solution

1
Analyze the investigator's objectives.
The goal is to test two independent interventions, assess their individual main effects, and determine if there is a synergistic effect (interaction) when used together.
Identifying the specific hypotheses to be tested dictates the required structural elements of the study design.
2
Evaluate the constraints.
The design must achieve these goals using the most statistically efficient sample size possible.
Efficiency eliminates designs that require multiple separate trials or those that inherently inflate required sample sizes (like cluster randomization).
3
Select the optimal design matching the parameters.
A 2x2 factorial design randomizes participants to four groups (Drug only, Protocol only, Both, Neither).
This design utilizes the entire cohort to calculate main effects and is the standard methodology for evaluating interaction (synergy).

Key Concept

Factorial clinical trial design
Estimated Time:1m 30s
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Topics

Study Design

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