Long-term probabilistic forecasts of activity mitigation in English hospitals: a national elicitation exercise providing an outside view based on judgements of experts in support of the New Hospital Programme.

Abstract

The planning process for a new hospital relies on assumptions about future levels of demand. Typically, such assumptions are characterised by point estimates, the flaw-of-averages, base-rate neglect and overoptimism from an inside view. To counteract these limitations, we elicited an outside view of probabilistic forecasts based on judgements of experts about the extent to which various types of hospital activity might be mitigated over 20 years, in support of the New Hospital Programme (NHP) in the English National Health Service. A prospective online elicitation exercise, over two rounds, to forecast the reduction (0% no reduction to 100% total reduction) in 77 types of hospital activity across England via five types of activity mitigation: outpatient attendance avoidance (n=8); inpatient admission avoidance (n=31); A&E attendance avoidance (n=12); outpatient delivery mode (n=4); inpatient length of stay reduction (n=22) and eight types of activity groups.Primary outcomes are the aggregated forecasts representing the percentage reduction (0%-100%) in hospital activity across England based on 'surprisingly low' (10th percentile-P10) to 'surprisingly high' (90th percentile-P90) forecasts from 17 experts. We had 657 forecasts from 17 experts. The most pessimistic forecast was for inpatient avoidance of frail elderly admissions (mean 5.71%, P10=0.43%, P90=16.40%). The most optimistic forecast was for inpatient admission avoidance for vascular surgery (mean 48.27%, P10=19.82%, P90=78.57%). The overall (n=77) aggregate means ranged from a low of 5.71% to a high of 48.27% with an average width of 50.08%. Experts highlighted mainly four types of mitigation mechanisms-prevention, displacement, quality improvement and de-adoption. A national elicitation exercise has provided long-term aggregate forecasts across England that make explicit the wide variation and uncertainty associated with future mitigation activities from an outside perspective. These aggregate forecasts may now be incorporated into the NHP, providing a more robust foundation for planning.