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attrition, intention to treat, randomized controlled trials



  1. Polit, Denise F.
  2. Gillespie, Brigid M.


Background: In randomized controlled trials (RCTs), the intention-to-treat (ITT) principle, which involves maintaining study participants in the treatment groups to which they were randomized regardless of postrandomization withdrawal, is the recommended analytic approach for preserving the integrity of randomization, yet little is known about the use of ITT in nursing RCTs.


Objectives: The purpose of this study was to describe the extent to which nurse researchers who conduct RCTs state that they have used ITT, the extent to which they adhere to ITT principles, and the methods they use to handle missing data.


Methods: Data regarding ITT analysis, participant flow, rates of attrition, and methods of handling missing data were extracted and coded from a consecutive sample of 124 RCTs published in 16 nursing journals in 2007 and 2008.


Results: ITT was declared in only 15.3% of the nursing RCTs, and a definition of ITT was offered in fewer than half of these studies. On the basis of the authors' descriptions of analytic procedures, it was concluded that 10.5% of those claiming ITT use had used a per-protocol analysis rather than an ITT analysis. Overall, 46.8% of the RCTs were classified as having either a classic or a modified ITT analysis, indicating that many nurse researchers are not stating their actual adherence to ITT, despite advice to do so in the Consolidated Standards of Reporting Trials guidelines.


Conclusions: Nurse researchers conducting RCTs should be more diligent in following the Consolidated Standards of Reporting Trials guidelines about ITT, documenting ITT use in their reports, clarifying their definition of ITT, and presenting flowcharts that describe subject flow. Readers of nursing reports, in evaluating evidence from RCTs, should not rely on stated use of ITT but should examine how analyses were conducted.