Poor control of chronic clinical conditions, particularly when coupled with functional limitations, mental health conditions, and social risk factors, can result in potentially preventable or modifiable overreliance on the ED and hospital. Interventions for high-need, high-cost (HNHC) patients aim to improve their quality of care and health outcomes while reducing their healthcare use and cost. The goal of this review is to provide actionable evidence to help identify HNHC patients and determine the causal mechanisms and effectiveness of complex interventions that intend to improve HNHC patient and healthcare system outcomes.

Main points

• Data from claims and health records can identify characteristics associated with being high-need, high-cost (HNHC) patients but are limited in selecting specific patients who are most appropriate for care management interventions.
• Much work remains in distinguishing preventable and modifiable high healthcare use from high use more generally.
• Identifying and targeting HNHC patients for interventions to change their healthcare use requires capturing their medical and social complexities. Building and maintaining trusting, caring relationships between HNHC patients and care providers underpins successful patient interventions. Both patients and care providers require support and practical resources to foster an effective relationship.
• We found moderate to low strength of evidence (SOE) that emergency department (ED)–based, primary care–based, and home-based care models are associated with reduced use of healthcare services; low SOE that ED, ambulatory intensive caring unit (aICU), and primary care models are associated with reduced costs; and low SOE that system-level transformation and telephonic/mail models are not associated with use or cost differences.

Background. In the United States, patients referred to as high-need, high-cost (HNHC) constitute a very small percentage of the patient population but account for a disproportionally high level of healthcare use and cost. Payers, health systems, and providers would like to improve the quality of care and health outcomes for HNHC patients and reduce their costly use of potentially preventable or modifiable healthcare services, including emergency department (ED) and hospital visits.

Methods. We assessed evidence of criteria that identify HNHC patients (best fit framework synthesis); developed program theories on the relationship among contexts, mechanisms, and outcomes of interventions intended to change HNHC patient behaviors (realist review); and assessed the effectiveness of interventions (systematic review). We searched databases, gray literature, and other sources for evidence available from January 1, 2000, to March 4, 2021. We included quantitative and qualitative studies of HNHC patients (high healthcare use or cost) age 18 and over who received intervention services in a variety of settings.

Results. We included 110 studies (117 articles). Consistent with our best fit framework, characteristics associated with HNHC include patient chronic clinical conditions, behavioral health factors including depression and substance use disorder, and social risk factors including homelessness and poverty. We also identified prior healthcare use and race as important predictors. We found limited evidence of approaches for distinguishing potentially preventable or modifiable high use from all high use. To understand how and why interventions work, we developed three program theories in our realist review that explain (1) targeting HNHC patients, (2) engaging HNHC patients, and (3) engaging care providers in these interventions. Theories identify the need for individualizing and tailoring services for HNHC patients and the importance of building trusting relationships. For our systematic review, we categorized evidence based on primary setting. We found that ED-, primary care–, and home-based care models result in reduced use of healthcare services (moderate to low strength of evidence [SOE]); ED, ambulatory intensive caring unit, and primary care-based models result in reduced costs (low SOE); and system-level transformation and telephonic/mail models do not result in changes in use or costs (low SOE).

Conclusions. Patient characteristics can be used to identify patients who are potentially HNHC. Evidence focusing specifically on potentially preventable or modifiable high use was limited. Based on our program theories, we conclude that individualized and tailored patient engagement and resources to support care providers are critical to the success of interventions. Although we found evidence of intervention effectiveness in relation to cost and use, the studies identified in this review reported little information for determining why individual programs work, for whom, and when