Simulating waiting list management.

Patients' experiences of waiting for treatment have changed dramatically in recent years in the United Kingdom's National Health Service. There has been a substantial reduction in the mean wait but the characteristics of the distributions have also changed significantly, implying a change in priorities and waiting list management. Simulations are often used to assess proposals for investment and reorganisation that might affect waiting time. However, a more realistic model incorporating waiting list management behaviour is needed since empirical distributions of waiting times indicate that a first-in-first-out model is not valid. This study develops a model of waiting list management that includes an explicit measure of priority associated with the patient's wait compared to a specified target. The model can generate a range of behaviours, from the near negative exponential distributions associated with some historic examples of waiting list management, through to the well defined modes of a rigid first-in-first-out system. In one illustration of the use of the waiting list management model, the impact of the seasonal variations in demand and supply was explored. Simulation experiments demonstrated the consequent seasonality in waiting times, implying a need for care when monitoring progress towards any targets.