Ten-year follow-up of ARIMA forecasts of attendances at accident and emergency departments in the Trent region.

Forecasting models for first, return and total attendances at accident and emergency (A&E) departments and yearly forecasts were developed ten years ago for all the health districts in the Trent region in England. The one-yearly forecasts had been checked against the 1986 actual figures and found accurate for first attendances but less accurate for return attendances. The forecasts for 1993 and 1994 were much further from the actual figures than the 1986 forecasts, with an increasing bias towards overestimation, particularly for reattendances. Whether a first attender is reviewed at a further visit may depend on local medical policy, which itself may vary with personnel changes. The one-off original ARIMA forecasts for new attendances for 1994 were no better than the district projections made in 1984, but they were better than the Trent Regional Health Authority guidelines. The ten-year strategic plan for Trent Regional Health Authority overestimated the increase in the number of first attendances at A&E departments in the Trent region. The forecasting methodology on which it was based could be improved by incorporating the ARIMA method into planning at the health district level. New forecasts or updated ones need to be calculated yearly.