Out-of-hours primary care (OOH-PC) has been introduced in many health systems to reduce non-urgent emergency department (ED) use. While prior studies suggest potential efficiency gains, economic evaluations rarely stratify outcomes by patient risk, limiting policy relevance. This study assesses the cost-effectiveness of diverting low-risk patients from ED to OOH-PC.

Compare direct medical costs, time spent at the facility, and hospitalization probability across risk and care setting subgroups from a societal perspective.

We analysed data from a cluster-randomized trial conducted in Belgium that examined a nurse-led triage system. Under the study trial’s extended Manchester Triage System (eMTS) protocol, patients eligible for primary care were assigned to OOH-PC and are referred to in our study as low-risk, while those assigned to the ED are defined as high-risk. To complement previous work, we stratified costs and effects by risk group. Mixed-effects regression models estimated costs, time at the facility, and hospitalization, with bootstrap confidence intervals. We also calculated the incremental net monetary benefit (INMB).

Treating low-risk patients at the OOH-PC instead of at the ED reduced costs by €24 (€14–€39) per patient, shortened the time spent at the facility by 69 (52–94) minutes. From a societal perspective, the average INMB was €49.5 per low-risk patient. Aggregately, we estimated that the 37 intervention weekends in 2019 led to an average saving of €14,136 in direct medical costs and cumulative time savings of 28 days.

Diverting low-risk patients from the ED to OOH-PC resulted in cost- and time-savings for low-risk patients at the study site. These findings highlight the potential to improve out-of-hours healthcare delivery to maximize benefits for patients and healthcare systems, although confirmation in other healthcare settings is required before wider implementation.