Veteran health information exchange volume and 30-day readmissions, avoidable hospitalizations, and in-hospital mortality: evidence from community and Veterans Health Administration direct care.

Abstract

To determine whether a greater volume of health information exchange (HIE) between care delivery systems improves patient outcomes and whether effects differ between community care and Veterans Health Administration (VHA) direct care settings. We used electronic health record data for all VHA enrollees from January 2022 to December 2023 (3144 medical center-months; 2.4 million patients per month). HIE volume, the number of unique patient-days with completed exchanges, was our key explanatory variable. Primary outcomes were 30-day readmissions, avoidable hospitalizations, and in-hospital mortality. We instrumented for HIE volume using each medical center's count of organizational exchange partners and estimated models overall and by care setting with medical center and month fixed effects and direct patient volume controls. In community care, a 1-SD increase in HIE volume was associated with 4.07 fewer 30-day readmissions (95% CI, -4.62 to -3.51), 1.45 fewer avoidable hospitalizations (95% CI, -2.84 to -0.06), and 0.25 fewer inpatient deaths (95% CI, -0.44 to -0.06) per medical center per month. In VHA direct care, the same increase in HIE volume was associated with 7.07 additional readmissions (95% CI, 6.46-7.67) and 0.19 additional inpatient deaths (95% CI, 0.03-0.35), with no significant impact on avoidable hospitalizations (95% CI, -0.96 to 1.68). Setting-specific effects may stem from asymmetric content (longitudinal histories outbound from VHA, episodic summaries inbound to VHA), asymmetric interfaces (modern community EHRs vs VHA's Joint Legacy Viewer), and HIE-enabled reclamation of community patients into VHA. More work is needed to disentangle these mechanisms.