Community Need Index (CNI): a simple tool to predict emergency department utilization after hospital discharge from the trauma service.

Background: Emergency department (ED) visits after hospital discharge may reflect failure of transition of care to the outpatient setting. Reduction of postdischarge ED utilization represents an opportunity for quality improvement and cost reduction. The Community Need Index (CNI) is a Zip code-based score that accounts for a community's unmet needs with respect to healthcare and is publicly accessible via the internet.