Percent total attrition: a poor metric for study rigor in hosted intervention designs

Abstract

Health behavior interventions delivered at point of service include those that yoke an intervention protocol with existing systems of care (e.g., clinical care, social work, or case management). Though beneficial in a number of ways, such "hosted" intervention studies may be unable to retain participants that specifically discontinue their use of the hosting service. In light of recent practices that use percent total attrition as indicative of methodological flaws, hosted interventions targeting hard-to-reach populations may be excluded from consideration in effective intervention compendiums or research synthesis because of high attrition rates that may in fact be secondary to the natural flow of service use or unrelated to differential attrition or internal design flaws. Better methods to characterize rigor are needed.

FIGURE 1

Participant flow in hosted intervention designs with suggested profile of outcomes. Note. ITT = intent-to-treat analysis. With excellent measurement retention or intensive retention strategies, some of strata 2 would be populated by those who had no missing data but had nonetheless discontinued their use of the hosting service. If sufficient in number, this group could be compared with other participants to determine the extent to which aspects of study methods or the intervention may have promoted study engagement. Note as well that appropriate methods for representing missing data in each analysis are assumed.

FIGURE 2

Example of profile approach for a hypothetical study of an adherence intervention delivered at point of HIV clinical care. Note: ITT = indent-to-treat analysis.