Delivery system emergency department capacity and its effect on nonsystem service utilization.

Background: Emergency department (ED) use is often seen as a source of excess health care spending, prompting managers to limit ED capacity in their health systems. However, if limited ED capacity in a delivery system leads patients to seek emergency care elsewhere, then health care quality and efficient management may be compromised within the system.

Objective: The objective of this study was to explore the effect of the Veterans Health Administration (VHA) in-house ED clinician capacity on VHA community care (CC) ED claims.

Methods: We used administrative data from the VHA to identify CC ED claims and Department of Veterans Affairs emergency physician (EP) capacity for 2014-2019. We used quasi-experimental instrumental variables approach with two different instruments: percent weekday federal holidays and VHA EP full-time equivalents (FTEs). We controlled for VHA ED variables such as ED wait times (door to triage, door to doctor, and door to admission) and demand variables such as alternative insurance coverage, driving time to VHA care, and demographic variables (employment, age, household income, race, gender, and VHA priority status).

Results: After instrumenting for capacity with percent weekday federal holidays, we found that one clinic-day capacity (one 8-h ED shift) per 10,000 enrollees increase at the VHA ED will result in a reduction of 61 CC ED claims per 10,000 enrollees. After instrumenting for capacity with EP FTE, we found that one clinic-day capacity (one 8-h ED shift) per 10,000 enrollees increase at the VHA ED will result in a reduction of 48 CC ED claims per 10,000 enrollees. Both of these results are statistically significant at p < 0.001.

Conclusions: Our findings imply that offering more in-house ED care, in the form of clinician capacity, can substantially reduce out-of-system ED use. The results may be of interest to integrated health care system managers who prefer their patients to stay within network.