Heterogeneity of Treatment Effect in a Randomized Trial of a Communication Intervention

Abstract

Context: Interventions to promote serious illness conversations have shown promise in promoting high-quality care. However, in randomized trials, some participants may benefit more from the intervention than others.

Objectives: To examine heterogeneity of treatment effect and identify subgroups of patients with serious illness who might benefit most from interventions to enhance communication about goals of care.

Methods: We used data from a multi-center cluster-randomized trial evaluating a communication intervention to increase goals-of-care discussions in the outpatient setting. Patients (n = 249 intervention, n = 288 usual care) had serious illness with an expected median survival of two years. Using model-based recursive partitioning, we tested heterogeneity of the intervention's effect on the occurrence of patient-reported goals-of-care discussions, electronic health record documentation of goals-of-care discussions, patients' ratings of quality of communication, and patients' symptoms of psychological distress at three and six months.

Results: We found two significant interactions. For patients' overall rating of clinician communication (n = 251), the intervention effect was positive for patients with higher household income, but not those with lower income (P < 0.001). For patients' symptoms of depression at six months (n = 288), the intervention was associated with fewer symptoms of depression among those whose self-assessed health was poor, but not among those with fair to excellent health (P < 0.001).

Conclusions: Identifying heterogeneity of treatment effect can be a valuable exercise following completion of a randomized trial. Interactions between the intervention and patient income and self-assessed health suggest these factors could be used to design more effective interventions to enhance communication about goals of care.

Keywords: Communication; Goals of care; Heterogeneity; Randomized trial.