Optimizing number and timing of appointment reminders: a randomized trial.

Objectives: To compare missed appointment rates for patients receiving a single reminder either 3 days prior to a primary care visit, 1 day prior to the visit, or both 3 days and 1 day prior to the visit.

Study Design: Three-armed randomized controlled trial.

Methods: Text messages or interactive voice response calls were sent to patients with appointments at 25 primary care clinics in an integrated delivery system.