A study is performed to compare the effect of tramadol when compared to placebo for painful polyneuropathy. Fifty patients are selected and randomly allocated to 1 of 2 treatment sequences: Tramadol followed by placebo, or placebo followed by tramadol. The initial treatment period is delivered for 4 weeks followed by an interim 1-week washout phase, after which the second treatment period is delivered for an additional 4 weeks. After each treatment period, patients use a 10-point numeric scale to rate pain, paresthesia, and tenderness. Which of the following best describes this study design?

Question

A study is performed to compare the effect of tramadol when compared to placebo for painful polyneuropathy.  Fifty patients are selected and randomly allocated to 1 of 2 treatment sequences:  Tramadol followed by placebo, or placebo followed by tramadol.  The initial treatment period is delivered for 4 weeks followed by an interim 1-week washout phase, after which the second treatment period is delivered for an additional 4 weeks.  After each treatment period, patients use a 10-point numeric scale to rate pain, paresthesia, and tenderness.  Which of the following best describes this study design?

Quizplus · Accepted Answer

11ec160b_372e_5fc3_9249_05ed6dd7a01a_MD0001_00 In this example, patients are allocated to 1 of 2 treatment groups: Group A receives placebo followed by tramadol and Group B receives tramadol followed by placebo. After the initial 4-week treatment period and the 1-week washout phase, the treatments are switched and delivered for an additional 4 weeks. This is consistent with a crossover study, in which subjects are randomly allocated to a sequence of 2 or more treatments given consecutively. The simplest model is the AB/BA type of study in which half of the subjects are allocated to the AB study arm and receive treatment A followed by treatment B, while the other half of the subjects are allocated to the BA study arm and receive the same treatments but in reverse order. In this way, crossover trials allow the patients to serve as their own controls. The principal drawback of crossover trials is that the effects of one treatment may carry over and alter the response to a subsequent treatment. To avoid this, a washout phase (no treatment) is often added between treatments. The washout period is designed to be long enough to allow the effects of prior treatment to wear off. (Choice A) A case-control study is designed by selecting patients with a particular disease (cases) and without that disease (controls), then determining their past exposure status to >1 risk factors believed to be associated with the disease of interest. (Choice B) A case series is a descriptive study that tracks patients with a known condition (eg, a particular exposure, risk factor, or disease) to document the natural history or response to treatment. Unlike a case-control study, a case series is a descriptive study that cannot quantify statistical significance. (Choice D) A cross-sectional study is also known as a prevalence study. It is characterized by the simultaneous measurement of exposure and outcome. It is a snapshot study design that frequently uses surveys. These studies are relatively inexpensive and easy to perform. (Choices E and F) Prospective cohort studies identify 2 groups of individuals (ie, cohorts), based on their exposure status to a risk factor. These 2 cohorts are then followed over time to assess development of the disease of interest. Sometimes the exposure status is determined retrospectively, typically using medical records, and patients are tracked from the point of exposure onward. Educational objective: In a crossover study, subjects are randomly allocated to a sequence of 2 or more treatments given consecutively. A washout (no treatment) period is often added between treatment intervals to limit the confounding effects of prior treatment.

A Study Is Performed to Compare the Effect of Tramadol