Reductions in emergency department presentations associated with opioid agonist treatment vary by geographic location: A retrospective study in New South Wales, Australia

Introduction and Aims It is not known if the reduction in ED use during periods of OAT occurs across urgent and low acuity presentations. We aimed to compare the incidence and costs of urgent and low acuity ED presentations of people with opioid use disorder (OUD) in and out of opioid agonist treatment (OAT). Design and Methods This was a retrospective cohort study (N=24,875), using linked administrative health data from New South Wales (NSW), Australia. Urgent and low acuity ED incidence and associated costs were calculated for periods in and out of OAT. GEE models estimated the adjusted incidence rate ratio (IRR) for ED presentations. Average costs per person-day were calculated with bootstrap confidence intervals. Results Incidence of urgent presentations was lower in OAT compared to out of OAT [IRR (95%CI): 0.65 (0.61-0.69)]. In major cities, low acuity presentations were lower during OAT compared to timeout of OAT [IRR (95%CI): 0.82 (0.70-0.96)], in regional/remote areas, low acuity presentations were higher during OAT [IRR (95%CI): 2.65 (1.66-4.21)]. In major cities, average costs for low acuity presentations in OAT were 28% lower atA$0.50 (95%CI: A$0.48-A$0.52) and A$0.69 (95%CI: A$0.66-A$0.71) out of OAT, but 103% higher in regional/remote NSW, at A$2.12 (95%CI: A$1.91-A$2.34) in OAT and A$1.04 (95%CI: A$0.91-A$1.16) out of OAT. Discussion and Conclusions OAT was associated with reductions in urgent ED presentations and associated costs among people with OUD. Geographical variation was evident for low acuity ED presentations, highlighting the need to increase access to OAT in regional/remote areas.