An Analysis of ED Utilization in California Medicaid Enrollees

The Affordable Care Act expanded eligibility for the Medicaid program with the hope of enrolling millions of low-income U.S. residents who could not access insurance.   California was one of the states that chose to expand.  Researchers at the University of California-San Francisco conducted a study that investigated the trends in the association between insurance coverage and usage of emergency departments among adults 18-64 from 2005 through 2010.  They found that ED utilization in California increased at a faster rate for adult Medicaid enrollees than for the privately insured or the uninsured.

Other studies attempt to shed insight on why Medicaid enrollees frequently visit the emergency department.  Some show that Medicaid enrollees have trouble accessing their primary care doctor and receiving adequate primary care.  Some document issues such as “fragmented care as a result of mental illness and homelessness, high medical comorbidity, untreated substance use, pain diagnoses, physician reliance on EDs for follow up care, and difficulty getting timely prescription refills.”

Medicaid programs have initiatives to reduce ED utilization in Medicaid enrollees, such as diverting non-emergent patients to lower cost settings, charging co-payments for non-emergency ED use, and focusing efforts on super-utilizers.   The state of Washington, through its “ER is for Emergencies” coalition, focuses on frequent users, provides patient education, improves access to primary care, and encourages physician participation in the state’s prescription monitoring program.   The result is a nearly 10 percent reduction in the rate of ED visits and a savings of almost $34 million in Medicaid fee-for-service emergency care costs.

The state of California’s Office of Statewide Health Planning and Development released a dataset of emergency department encounters by expected payer (including Medi-Cal) from 2005 through 2015.  I analyzed the data to answer the following questions:

  • Does the data show an increase in ED utilization in California from the rollout of the Affordable Care Act (Q4 2013 through Q4 2015)?
  • Which EMS Service levels (basic, comprehensive, standby) and counties comprised the highest proportion of the utilization?

I carried out three steps.  First, I added the number of encounters at the levels of quarter and year, from Q4 2013 through Q4 2015.  Second, I added the number of encounters at the levels of quarter, year, and EMS Service Level, from Q4 2013 through Q4 2015.  Third, I added the number of encounters at the levels of quarter, year, and county, from Q4 2013 through Q4 2015.  I used SAS University Edition to carry out my analyses.

The California Emergency Medical Services Authority defines basic, standby, and comprehensive emergency services as follows:

  • The basic service level “provides emergency medical care in a specifically designated part of the hospital that is staffed and equipped at all times to provide prompt care for any patient presenting urgent medical problems.”
  • The standby service level “provides emergency medical care in a specially designated part of the hospital that is equipped and maintained at all times to receive patients with urgent medical problems and is capable of providing physician service within a reasonable time.”
  • The comprehensive service level “provides diagnostic and therapeutic services for unforeseen physical and mental disorders that, if not properly treated, would lead to marked suffering, disability, or death. The scope of services in comprehensive with in-house capability for managing all medical situations on a definitive and continuing basis.”

The number of encounters increased from almost 865,000 in Q4 2013 to almost 1.4 million in Q4 2015, a 67% increase.

ED utilization - Overall Quarterly Trend 2

The number of encounters where the ED in which the encounter took place was licensed for basic emergency services increased from almost 797,000 in Q4 2013 to almost 1.2 million in Q4 2015, a 67% increase.   Encounters in emergency departments licensed for basic emergency services comprised over 90% of the total.

ED utilization - Service Level Trend

The number of encounters that took place in L.A. County jumped from almost 222,000 in Q4 2013 to almost 329,000 in Q4 2015, a 52% increase.   Encounters that took place in L.A. County accounted for roughly 25% of the total.

ED utilization - County Level Trend 2

The results indicate a dramatic increase in ED utilization in California since the rollout of the Affordable Care Act.  It stemmed from the California Medicaid program’s utilization surge, during which California added 4.5 million enrollees between Q4 2013 and Q4 2015.  The observation that the majority of encounters took place in EDs licensed for basic emergency services supports the studies that show the difficulties Medicaid enrollees face in obtaining access to primary care.  In addition, L.A. County, the county where the most encounters took place, has the largest burden of treating Medicaid enrollees in California.  L.A. County has multiple hospitals, health plans, provider groups, and other facilities available to treat this population.  However, more research on Medicaid ED utilization in L.A. County and its impact on quality and costs is needed.

The Office of Statewide Health Planning and Development did not indicate whether the dataset was restricted to adults.  The UCSF study, restricted to adult Medicaid enrollees, states the rate of ED visits increased by 13.8 percent from 2005 through 2010.  Also, there is some question over the use of expected payer as the indicator for the insurance a patient possesses.   The dataset didn’t have any information on copays or eligibility.

California Medicaid enrollees have been utilizing the ED at a high rate since the ACA rollout, but the specific rate for adults is unknown in the dataset provided by the Office of Statewide Health Planning and Development.   The data support previous studies’ findings on Medicaid enrollees’ lack of access to primary care.   Los Angeles County seems to be the center of about one fourth of the ED utilization, thus it has the most responsibility for treating Medicaid patients that come through the ED. More research is needed on the characteristics of Medicaid patients who use the ED frequently and how they differ from the privately insured and uninsured.


  1. Renee H, Brownell J, Wilson S, Gordon N, Baker L. Trends in Adult Emergency Department Visits in California by Insurance Status, 2005-2010.  JAMA 2013; 310(11): 1181-1183.
  2. Revisiting Emergency Department Use in Medicaid. Medicaid and CHIP Payment and Access Commission Web site.  https://www.macpac.gov/wp-content/uploads/2015/01/MACFacts-EDuse_20....  Accessed May 13, 2016.
  3. Daly R. ED Use Surges Among California Medicaid Enrollees.  Healthcare Financial Management Association Web site.  https://www.hfma.org/Content.aspx?id=48018. Accessed May 13, 2016.
  4. Emergency Department Encounters by Expected Payer, 2005-2015. HealthData.gov Web site.  http://www.healthdata.gov/dataset/emergency-department-encounters-e....  Updated May 9, 2016.  Accessed May 13, 2016.
  5. Office of Statewide Health Planning and Development. Healthcare Atlas.  http://gis.oshpd.ca.gov/atlas/topics/er_dashboard.  Accessed May 13, 2016.

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Tags: analytics, data, healthcare


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