Attrition Effects
Attrition refers to the loss of participants in a study. Attrition effects refers to a type of systematic error and associated bias that arises from systematic differences in the way participants are lost from a study1.
Random attrition overall results in a reduction in overall data for analysis, which will not result in attrition effects1.
A differential loss of pts from one group to another d/t reasons that might impact treatment outcomes such as poor motivation or adverse treatment effects. -Dr. Monroe
Monroe stated this, but I am unsure how this can cause poor motivation if the patients are blinded.
Determining Significant Attrition
| Loss to follow-up | Study Impact |
|---|---|
| \(\leq 5\%\) | Unlikely to introduce bias1 |
| \(5-20\%\) | Might be a source of bias |
| \(20\%\) | Concerning possibility of bias |
Although this quick guide is useful, one should also distinguish between overall attrition rates and whether those without follow-up data are different from those with data1.
Prevention
An intention-to-treat analysis should be used to mitigate attrition effects.