Comparative effectiveness trials in asthma – how will I recognize one?

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Purpose of review

Comparative efficacy trials are designed to evaluate the harms and benefits of health care in a research environment. There is increasing interest in the results of comparative effectiveness trials, which are intended to fill gaps in evidence to inform decision-making in real-life clinical environments. The objective of this report is to review various tools to classify trials along the efficacy to effectiveness continuum.

Recent findings

Three tools [Pragmatic-Explanatory Continuum Indicator Summary (PRECIS), PRECIS-2, and PRAgmatic Clinical Trial Assessment Scale (PRACTAS)] are available that use a star diagram to illustrate where each element of a clinical trial design falls along the efficacy to effectiveness continuum (e.g., selectivity of eligibility criteria, supports to promote participant adherence). The number and type of design element to be classified varies (e.g., 10 elements for PRECIS and PRACTAS vs. nine elements for PRECIS-2; only the PRACTAS tool includes stakeholder engagement). There is substantial interrater reliability when using all three tools and interrater reliability varies across the different design elements (intraclass correlation of coefficient 0.4–0.8).


The PRECIS, PRECIS-2, and PRACTAS tools are options when classifying trials along the efficacy to effectiveness continuum. Researchers and decision-making stakeholders are likely to disagree about the extent to which clinical trials employ efficacy or effectiveness designs.

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