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The association between area deprivation index and emergency department discharge rates and revisits

Hospital care represents one of the largest and fastest growing components in U.S. national health spending,1 and the majority of these hospitalizations originate in the emergency department (ED).2 Marked interhospital variability exists in admission rates for certain conditions,2,3 suggesting opportunity to reduce health care expenditures by reducing potentially avoidable admissions. This serves as the target of a novel alternative payment model recently endorsed by the U.S. Secretary for Health and Human Services; the proposed Acute Unscheduled Care Model targets reducing avoidable admissions paired with improving safe discharge planning.3 As EDs may be incentivized toward discharging patients, it is essential to better understand drivers of disposition variability and characterize atrisk populations. Previous studies have found that patientand hospitallevel factors alone do not explain admission rate variability,2 suggesting that other factors, such as community resources, may contribute.4 Community resources, or lack thereof, may also be associated with adverse patient outcomes,5 especially after the potentially higherrisk decision to discharge rather than admit a patient from the ED.3 Our study objective was to assess association between socioeconomic deprivation, riskadjusted ED discharge rates, and ED revisit risk. We performed a retrospective observational analysis of 2017 nonpublic inpatient and ED administrative data from the California Office of Statewide Health Planning and Development (OSHPD). This allpayer database includes patient record linkage numbers to allow for revisit tracking and includes all nonfederally licensed hospitals and EDs in California. Our study was limited to adult patients, 18 years of age or older, who presented to the ED for one of six medical conditions previously identified as having significant variability in ED discharge rates: altered mental status, chest pain, chronic obstructive pulmonary disease (COPD) exacerbation, skin and soft tissue infection, syncope, and urinary tract infection.2,3 We identified these conditions by primary discharge diagnosis using previously described methods.2,3 We excluded EDs with fewer than 10,000 adult patient visits in 2017 to ensure an adequate sample. We also excluded visits with dispositions of left against medical advice, left before visit completion, or other/unknown disposition and without record linkage numbers because of the inability to precisely classify and measure outcomes for these visits. To approximate socioeconomic deprivation, we used the 2015 national Area Deprivation Index (ADI) of the hospital location. The ADI is based on a measure developed originally by the U.S. Health Resources & Services Administration. It incorporates income, education, employment, and housing data to assign each census block percentile based on relative socioeconomic deprivation.5 The ADI has previously been utilized for federal disparities reduction programs,6 and it has been studied in association with readmission rates and ED utilization.5,6 For each condition, we used multivariable logistic regression to estimate hospitallevel discharge rates, adjusting for hospital, age, sex, payer, and Elixhauser comorbidity score. We then assessed for association between the ADI and adjusted ED discharge rate, using Spearman's correlation coefficient. We next identified hospitals that had both higherthanmedian ADI and higherthanmedian adjusted discharge rates for each condition. This set of hospitals was flagged as an “atrisk” hospital cohort for adverse outcomes, and we calculated and compared 30day allcause ED revisits for discharged patients between these atrisk hospitals and the remaining hospitals using Wilcoxon ranksum test. This study was granted human subject approval through the University of California San Francisco Institutional Review Board as an exempt protocol. Our study included 1,410,271 patient visits with a condition of interest to 271 hospitals. Study hospitals were primarily nonteaching, with only 10% reporting as teaching hospitals. Hospital ownership was mostly nonprofit (65%), with 14% of hospitals reporting government (state, city, county, or district) ownership and 21% reporting private ownership. Eighty six percent of hospitals were in a rural region. In 2017, 29% of study hospitals had 10,000 to 30,000 ED visits, 29% had 30,000 to 50,000 visits, 28% had 50,000 to 80,000 visits, and 14% had more than 80,000 visits. We found weakly positive correlations between adjusted discharge rate and ADI for COPD exacerbation, skin and soft tissue infection, and urinary tract infection (Spearman correlation coefficients of 0.19, 0.26, and 0.21, respectively, with p < 0.01). There was no significant association between adjusted discharge rate and ADI for altered mental status, chest pain, or syncope. We next assessed ED revisit rates for atrisk versus other hospitals. We found that there were small but statistically significant differences in median revisit rates for syncope and UTI, with atrisk hospitals having higher revisit rates relative to other hospitals (Table 1). We did not find a statistically significant association for the other conditions. Supervising editor: Dr. Kamna Balhara