Outpatient Appointment Scheduling Under Patient Heterogeneity and Patient No-Shows

Abstract

We study outpatient appointment block scheduling policies for single providers under conditions of patient heterogeneity in service times and patient no-shows. The objective is to find daily appointment schedules that minimize a weighted sum of patients' waiting time, the physician's idle time, and the physician's overtime. Compared to extant outpatient scheduling approaches, we contribute by suggesting new sequential block scheduling procedures grounded in actual outpatient clinic practices and in the successful Toyota Production System load smoothing approach, leading to effective appointment schedules when scheduling two heterogeneous patient types. Our block scheduling policy first assigns a sequence of different patient types given patient demand and service time information. The block scheduling policy then allocates repetitive blocks in a planning horizon. We first analyze the case with heterogeneous patient types and zero probability of no-shows. We propose an optimal scheduling approach for two patient types under a class of schedules where the physician's idle time is zero, before demonstrating that the multiple patient type problem is NP-Hard. We then extend our scheduling approach to incorporate patient no-shows. We find the approach works better than other methods when short service time patients have any no-show probability level and when long service time patients have moderate or lower no-show probability. Next, we adapt the approach to incorporate an overbooking strategy, to directly address and remediate patient no-shows. Using numerical experiments, we show that the overbooked block scheduling approach provides effective practical solutions. Finally, our block scheduling approach is adapted for scenarios where outpatient clinics use an open-access scheduling environment, where patients are allowed to make same-day appointments. Due to patient demand uncertainty in the open-access case, we again employ numerical experiments to compare our block scheduling policies against extant scheduling policies, finding our scheduling policies surpass the others. The paper contributes to scheduling literature by developing an innovative outpatient block scheduling approach that can be adapted for overbooking and open-access scheduling scenarios.