217 A Method for Stratifying Emergency Department Visits by Severity and Complexity: National Hospital Ambulatory Medical Care Survey Items

Abstract

Triage functions to quickly prioritize care and sort patients by anticipated resource needs. Despite widespread use of the Emergency Severity Index (ESI), there is still no universal standard for ED triage in the US. Thus, it can be difficult to objectively assess national trends in US ED acuity and resource requirements or to adjust for case mix between hospitals or regions. We sought to derive an emergency severity index from National Hospital Ambulatory Medical Care Survey (NHAMCS) survey items (NHAMCS-ESI) and to assess the performance of this index with respect to stratifying several outcomes, including hospital admission, waiting time, and overall length of stay (LOS). We also sought to compare NHAMCS-ESI to the “immediacy” variable, which is a NHAMCS measure that has been measured differently over time. We used data from the 2010-2015 NHAMCS, to create a measure of ED visit complexity based solely on variables available in NHAMCS. We used NHAMCS data on chief complaint, vitals, resources used (labs and imaging), interventions (eg, intubation) and pain level to group ED visits into 5 levels of acuity using a stepwise algorithm that mirrored ESI. First, patients who are in cardiac arrest, unresponsive, bradycardic, intubated, receiving CPR, or hypotensive, are level 1. Level 2 patients are those not meeting Level 1 who have certain chief complaints or vital sign abnormalities. Level 3 patients are defined by vital signs, pain, resources used, and chief complaints, and Level 4 and 5 patients are defined by resource utilization. We examined associations of NHAMCS-ESI with typical indicators of acuity such as waiting time, LOS, disposition. We also compared NHAMCS-ESI categorization with that given by the “immediacy” variable across all these outcomes. Visit counts used weighted scores to estimate national levels of ED visits. All analyses were conducted using Stata v.10 (College Station, TX). The NHAMCS ED visits represent an estimated 805,726,000 ED visits over this time period. NHAMCS-ESI categorized visits somewhat evenly, with most visits (42.5%) categorized as a level 3 (Figure 1). The categorization pattern is distinct from that of the “immediacy” variable within NHAMCS. Eighty-nine percent of admitted patients were categorized as NHAMCS-ESI Level 2-3. Median ED waiting times increased as NHAMCS-ESI levels decreased in acuity (from approximately 14 minutes to 25 minutes). Median LOS decreased as NHAMCS-ESI decreased from almost 200 minutes for Level 1 patients to nearly 80 minutes for level 5 patients. We derived NHAMCS-ESI, an objective tool that uses data available in NHAMCS to measure an ED visit’s complexity and resource use. This tool can be validated and used to compare complexity of ED visits across hospitals and regions and over time.