HSChange

Dispelling Myths About Emergency Department Use: Majority of Medicaid Visits Are for Urgent or More Serious Symptoms

Originally published by the Center for Studying Health System Change

Published: July 2012

Updated: April 6, 2026

HSC Research Brief No. 23

July 2012

Anna Sommers, Ellyn R. Boukus, Emily Carrier

Despite the widespread assumption that Medicaid beneficiaries routinely turn to hospital emergency departments (EDs) for non-serious care, the vast majority of ED visits by nonelderly Medicaid enrollees involve symptoms indicating urgent or more critical medical issues, according to a new national analysis by the Center for Studying Health System Change (HSC). Roughly 10 percent of ED visits by nonelderly Medicaid patients involve nonurgent symptoms, compared to approximately 7 percent among privately insured nonelderly individuals. Nevertheless, clear opportunities exist to create lower-cost care alternatives to emergency departments for both nonelderly Medicaid and privately insured populations.

To decrease emergency department utilization, policy makers should explore ways to promote the growth of care settings capable of rapidly addressing a high volume of potentially urgent health concerns. Initial efforts might target conditions that drive significant ED volume yet could feasibly be managed in less resource-heavy environments. For instance, diagnoses of acute respiratory infections, other common childhood infections, and injuries collectively represent roughly 53 percent of ED visits by Medicaid-covered children aged 0 to 12 and nearly 60 percent of ED visits by privately insured children in the same age range. Although some infections and injuries will be too severe for treatment outside an ED, lower-cost facilities offering a moderate level of care with prompt response times could likely reduce emergency department utilization.

Misconceptions About ED Use

Policy makers and health care providers regularly cite heavy reliance on hospital emergency departments by Medicaid patients as a major contributing factor to overcrowded EDs, extended wait times, elevated costs, and suboptimal chronic disease management. However, recent studies have debunked misconceptions that tie ED use directly to overcrowding, demonstrating that the majority of crowding actually stems from emergency patients who are admitted to the hospital but left waiting for an inpatient bed -- a phenomenon known as ED boarding -- rather than from a high number of nonurgent visits. (1) Additional research has corrected the erroneous belief that most ED users carry Medicaid coverage, lack insurance, or have no regular source of care. In reality, privately insured individuals account for the bulk of ED utilization, and those with higher incomes and a private physician as their usual care provider are the ones driving increases in ED visits over time. (2)

Other persistent misconceptions about Medicaid patients' ED utilization continue to shape policy decisions. In the face of state budget pressures, a number of Medicaid programs have attempted to curb ED visits by refusing payment for emergency care deemed unnecessary after the fact, raising patient cost-sharing requirements to discourage visits, and imposing penalties on patients for excessive ED use -- all grounded in the assumption that Medicaid beneficiaries frequently visit emergency departments for symptoms that could wait for evaluation by a primary care clinician. (3) Media coverage of so-called frequent flyers -- a small subset of individuals with hundreds of ED visits -- may have further reinforced prevailing views that Medicaid and uninsured patients routinely use emergency departments inappropriately. (4)

It is true that nonelderly Medicaid enrollees visit EDs at higher rates than nonelderly people with private insurance. In 2008, individuals aged 0 to 64 covered by Medicaid had 45.8 ED visits per 100 enrollees, compared with 24.0 visits per 100 nonelderly privately insured people, based on the most recently available data from the National Hospital Ambulatory Medical Care Survey (NHAMCS) (see Table 1 and Data Source). This pattern of elevated ED utilization among Medicaid enrollees holds true across all age groups -- children aged 0-12, teenagers and young adults aged 13-20, and adults aged 21-64. (5) However, the findings of this study reveal that Medicaid patients' higher ED visit rates are not driven disproportionately by minor health concerns when compared to those with private insurance.

Table 1: Emergency Department Visits per 100 Enrollees by Insurance Type and Age Group, 2008

All Nonelderly (Ages 0-64): Medicaid 45.8 visits per 100 enrollees; Private Insurance 24.0 visits per 100 enrollees.

Children (Ages 0-12): Medicaid 40.5 visits per 100 enrollees; Private Insurance 24.8 visits per 100 enrollees.

Teens/Young Adults (Ages 13-20): Medicaid 39.6 visits per 100 enrollees; Private Insurance 20.5 visits per 100 enrollees.

Adults (Ages 21-64): Medicaid 55.3 visits per 100 enrollees; Private Insurance 22.9 visits per 100 enrollees.

Sources: Center for Studying Health System Change analysis of 2008 National Hospital Ambulatory Medical Care Survey; Medicaid Statistical Information System, FY 2008; National Health Interview Survey, 2008.

The Difference Between Symptoms and Diagnoses

Two distinct types of clinical information from emergency department visits are generally used to characterize ED utilization -- the symptoms patients present with upon arrival and the diagnoses they receive at discharge. The urgency of presenting symptoms can shed light on why a patient chose an ED over another care setting, such as a physician's office or community clinic.

When patients arrive at the emergency department, triage staff evaluates the severity of their symptoms and determines how quickly each patient requires evaluation. The resulting measure of visit acuity was grouped for this analysis into five categories:

(1) Emergent -- patient must be seen immediately or within 15 minutes of arrival; (2) Urgent -- 15-60 minutes; (3) Semi-urgent -- 1-2 hours; (4) Nonurgent -- 2-24 hours; and (5) No triage or unknown triage.

Approximately 15 percent of both Medicaid and privately insured ED visits in the 2008 NHAMCS lack a triage acuity assignment for various recordkeeping reasons.

The second type of information used to characterize ED utilization is the physician's diagnosis following examination and evaluation in the emergency department. Diagnoses are frequently invoked as proof that many ED visits are medically unnecessary. However, relying on diagnoses to judge whether a specific patient truly needed emergency care is problematic because neither the triaging clinician nor the patient possesses the complete clinical picture until after the physician conducts an examination. (6) Diagnostic testing often rules out a more serious condition that was initially a concern during triage, and symptoms that seem alarming to patients can ultimately prove to have a straightforward, easily treatable cause (see box below regarding the urgency of symptoms). When analyzed at the population level rather than for individual patients, however, ED visit diagnoses serve as a valuable research tool for exploring how much emergency department care might be delivered in alternative settings.

This analysis employs both types of information -- symptoms and diagnoses -- to examine the composition of ED visits at the national level, with the important caveat that neither data source alone tells the whole story of why any particular patient sought emergency care. A visit's triage acuity may appear to be a misjudgment once a diagnosis is rendered because the triage classification reflects only the patient's presenting symptoms, while the diagnosis does not capture the urgency or severity of those symptoms. Furthermore, the NHAMCS data do not include details about the circumstances that prompted a patient to seek care, whether the patient has an established source of care, what guidance that provider may have offered, how long the symptoms had been present, or how the patient interpreted them.

Urgent or Nonurgent? It Depends...

Gauging the severity of a child's infection can be particularly challenging for parents because young children frequently cannot articulate the extent of their discomfort and may exhibit symptoms common to both harmless and dangerous conditions. For instance, infants may vomit, develop high fevers, and refuse to sleep in response to ear infections, which are relatively benign and straightforward to treat. Yet these same three symptoms can also occur with severe systemic infections that carry risks of dehydration and may require hospitalization. The actual diagnosis may not become clear until a clinician examines the child or until the symptoms progress further. When primary care providers cannot see a child promptly, an emergency department may be the only available option.

Adults, too, may seek rapid medical attention when symptoms are extremely uncomfortable, painful, or concerning, even if they are not life-threatening. Consider a woman suffering from a urinary tract infection (UTI) who may be unable to sleep due to severe discomfort and find it physically unbearable to wait days for a scheduled appointment. UTIs typically require a prescription antibiotic, and primary care providers may be reluctant to prescribe medication based solely on a telephone consultation. Depending on when symptoms began and when the next appointment slot is available, both the primary care clinician and the patient may reasonably conclude that an ED is the best place to seek treatment.

These examples highlight the inherent difficulty both patients and clinicians face in evaluating symptom urgency. The appropriateness of any given decision to seek care simply cannot be determined at the moment symptoms first appear. Significant gray areas and uncertainty exist around what risks patients face when deciding how long to wait for treatment and where to go. Medical conditions cannot be neatly sorted into urgent and nonurgent categories without clinical judgment from a trained provider.

Nonurgent ED Visits

Contrary to the prevailing belief that Medicaid beneficiaries frequently seek routine care in emergency departments, nonurgent visits account for only a modest share of the higher ED utilization among nonelderly Medicaid enrollees. In 2008, nonurgent visits represented 10 percent of Medicaid-paid ED visits and 7 percent of privately insured ED visits for nonelderly individuals at the national level (see Figure 1). By contrast, slightly more than half of both Medicaid and private visits were classified as emergent or urgent. Consequently, differences in nonurgent visit rates per 100 enrollees between Medicaid and privately insured patients explained just 13 percent of the overall gap in ED visit rates (findings not shown).

The bulk of the disparity in ED utilization between nonelderly Medicaid and privately insured patients is attributable to greater Medicaid use for urgent and semi-urgent symptoms (see Table 2). Medicaid patients visited EDs for urgent care -- requiring evaluation within an hour -- at a rate of 18.1 visits per 100 enrollees versus 9.6 visits per 100 among the privately insured. For semi-urgent visits -- where evaluation was needed within 1 to 2 hours -- the rate was 10.4 visits per 100 Medicaid enrollees compared to 5.5 visits per 100 for privately insured individuals. This same pattern persisted across all age groups but was especially pronounced among adults aged 21 to 64 (see Supplementary Table 1).

Figure 1: Distribution of ED Visits by Triage Acuity and Insurance Type, Nonelderly, 2008

Medicaid: Emergent 16%, Urgent 31%, Semi-urgent 18%, Nonurgent 10%, No triage/unknown 15%. Private Insurance: Emergent 17%, Urgent 30%, Semi-urgent 18%, Nonurgent 7%, No triage/unknown 15%. Note: Remaining percentages represent visits that do not fall into listed categories. Source: Center for Studying Health System Change analysis of 2008 NHAMCS.

Table 2: Emergency Department Visit Rates per 100 Enrollees by Triage Acuity and Insurance Type, Nonelderly, 2008

Emergent: Medicaid 7.4, Private 4.1. Urgent: Medicaid 18.1, Private 9.6. Semi-urgent: Medicaid 10.4, Private 5.5. Nonurgent: Medicaid 4.6, Private 1.6. No triage/unknown: Medicaid 5.3, Private 3.2. Source: Center for Studying Health System Change analysis of 2008 NHAMCS; MSIS FY 2008; NHIS 2008.

Children Often Have Worrisome Symptoms but Minor Conditions

A limited number of conditions account for more than half of all ED visits by both privately insured and Medicaid-covered children aged 0 to 12: acute respiratory infections, other common infections, and injuries. Combined, these conditions represented 53 percent of ED visits by children enrolled in Medicaid and nearly 60 percent of visits by privately insured children. Very few other diagnostic categories comprise a large enough proportion of visits that redirecting them to alternative care settings would meaningfully reduce emergency department patient volume. This provides compelling evidence that settings beyond emergency departments could manage a substantial share of pediatric visits, though such settings would need the capacity to treat 1) urgent and common childhood infections; and 2) minor or uncomplicated injuries.

Acute respiratory and other infections. Acute respiratory illnesses and other common infections -- including strep throat, bronchitis, ear infections, and conjunctivitis -- were the most frequently diagnosed conditions in ED visits by Medicaid-covered children aged 12 and younger, accounting for 31.4 percent of all visits (see Table 3). Among privately insured children of the same age, these conditions represented 22.1 percent of all visits. Although these findings might seem inconsistent with the low share of visits classified as nonurgent, diagnoses alone do not convey the severity of symptoms. Children may require prompt attention when they present with acute symptoms like high fever or lethargy yet subsequently need few resources for diagnosis and treatment. Approximately 65 percent of visits for these conditions in this age group were triaged as urgent or semi-urgent upon arrival at emergency departments. (7)

Children aged 0 to 12 with Medicaid coverage sought ED care for acute respiratory conditions and other common infections at a significantly higher rate than privately insured children -- 12.7 versus 5.5 visits per 100 enrolled children, respectively. In fact, these common infections alone accounted for half of the overall difference in visit rates between Medicaid and privately insured children. Children with Medicaid also visited EDs at higher rates for other infections -- such as pneumonia and influenza -- and other typically more serious respiratory diseases -- such as asthma -- which together represented an additional 16 percent of Medicaid-covered children's ED visits. These same patterns were observed among teens and young adults aged 13 to 20, although visit rates were considerably lower and payer-based differences less pronounced.

Among children under 18, the most common reason for physician office visits besides preventive care is acute respiratory infections, sinusitis, and bronchitis. (8) Nearly all children enrolled in Medicaid have a usual source of care, (9) and most physicians who treat children participate in Medicaid and the Children's Health Insurance Program (CHIP). (10) Therefore, given the urgency documented in ED visits for these conditions, challenges in obtaining timely access to these clinicians may explain why substantially more children with Medicaid turn to the ED for help.

Injuries. A full 38 percent of all ED visits by privately insured children aged 0 to 12 were related to injuries -- both urgent and nonurgent -- compared with 22 percent for Medicaid-covered children. There was no statistically significant difference in injury-related visit rates between the two payer groups -- 8.9 visits for private insurance and 9.8 visits for Medicaid per 100 enrollees -- indicating that barriers to primary care do not disproportionately affect injury care for children with Medicaid. The same pattern was observed among teens and young adults aged 13 to 20.

Certain injuries require emergency services, and in other instances, a primary care office may lack the appropriate resources -- such as suturing equipment -- or parents may not view primary care as the right setting for injury treatment. In any event, these factors do not appear to affect children with Medicaid disproportionately.

Table 3: Emergency Department Visits by Diagnosis Category, Children Aged 0-12, 2008

Acute Respiratory/Common Infections: Medicaid 31.4% of visits (12.7 per 100 enrollees); Private 22.1% of visits (5.5 per 100 enrollees). Injuries: Medicaid 22.0% (9.8 per 100); Private 37.7% (8.9 per 100). Other Infections (pneumonia, influenza): Medicaid 8.8% (3.6 per 100); Private 5.3% (1.3 per 100). Asthma/Respiratory Diseases: Medicaid 7.0% (2.8 per 100); Private 3.2% (0.8 per 100). Digestive Conditions: Medicaid 5.3% (2.2 per 100); Private 5.9% (1.5 per 100). Skin Conditions: Medicaid 4.7% (1.9 per 100); Private 3.7% (0.9 per 100). Nervous System/Sense Organs: Medicaid 3.6% (1.5 per 100); Private 4.4% (1.1 per 100). Other/Unclassified: Remaining percentages. Source: Center for Studying Health System Change analysis of 2008 NHAMCS.

Medicaid Adults Sicker

Nonelderly adults covered by Medicaid generally exhibit higher ED utilization across all medical conditions, reflecting well-documented health status differences compared to privately insured adults: greater illness burden, higher disease severity, and elevated rates of severe disability. (11) Adults aged 21 to 64 with Medicaid use emergency departments at more than double the rate of privately insured adults across all major diagnostic categories, including respiratory, digestive, musculoskeletal, and nervous system diseases. This same pattern was evident among teens and young adults aged 13 to 20, although across a smaller range of diagnostic groups.

Adults aged 21 to 64 with Medicaid were also three times as likely as their privately insured counterparts to have ED visits for diagnoses indicating potentially complex needs related to pregnancy and disabling conditions -- such as cerebral palsy, cardiomyopathy, and chronic hepatitis -- at 5.4 visits per 100 Medicaid enrollees compared with 1.5 visits per 100 privately insured enrollees. The wide variety of conditions driving ED utilization by nonelderly adults could pose challenges for alternative care settings seeking to accommodate these patients' urgent medical needs.

Multiple conditions. Medicaid patients aged 21 to 64 who visited EDs more frequently had a secondary diagnosis of a mental disorder than privately insured patients -- 6.1 versus 0.7 visits per 100 enrollees, respectively (findings not shown). Additionally, a greater proportion of nonelderly adult Medicaid ED visits involved more than one major diagnostic category -- for example, diabetes alongside congestive heart failure -- compared to privately insured individuals -- 27.1 percent of visits versus 19.5 percent, respectively (findings not shown). Individuals with multiple conditions frequently require rapid assessment of otherwise minor symptoms, such as dizziness or nausea, and the presence of multiple conditions can complicate evaluation and treatment while increasing the likelihood of hospitalization. (12)

Injuries. Injuries accounted for the largest share of ED visits by adults aged 21 to 64 in both payer groups -- 28.7 percent of Medicaid visits and 33.6 percent of privately insured visits. However, adults with Medicaid sought ED care for injuries at twice the rate of privately insured adults -- 15.9 visits versus 7.7 visits per 100 enrollees, respectively. Part of this elevated injury-related ED use among Medicaid patients may stem from their greater likelihood of disability -- for example, a person who uses a cane faces a higher risk of falling. (13)

Barriers to care. Nonelderly adults with Medicaid encounter barriers to primary and specialty care that likely contribute to their elevated ED utilization. A recent national study demonstrated that Medicaid-covered adults who visit EDs are significantly more likely to report obstacles to obtaining primary care compared to privately insured patients, even among those with an established primary care physician. (14) Moreover, limited resources at primary care practices can make it impractical to diagnose and treat even straightforward problems when symptoms are nonurgent. Only approximately one-third of primary care physicians serving a large percentage of adult Medicaid patients had X-ray equipment at their main practice in 2008, while fewer than half offered laboratory services. (15) Research has also linked higher ED utilization by Medicaid enrollees to primary care practices with fewer weekday evening hours or those lacking medical supplies for treating respiratory conditions, such as nebulizers and peak flow meters. (16)

Given that elevated ED utilization by adults aged 21 to 64 with Medicaid reflects a wide range of medical conditions, unmet demand for specialty care may also be a contributing factor. In 2008, only 53 percent of specialists nationwide were accepting all or most new Medicaid patients, compared to 87 percent accepting all or most new privately insured patients. (17) Adults with Medicaid coverage reportedly face difficulty accessing numerous medical specialties, particularly orthopedics, gastroenterology, neurology, and dermatology. (18) Limited access to specialty care could fuel high ED utilization by leaving patients no alternative source of care other than emergency departments for acute and ongoing symptoms related to chronic conditions.

An insufficient supply of inpatient psychiatric beds also contributes to prolonged lengths of stay in EDs for patients with psychiatric needs, (19) likely reinforcing perceptions that individuals with mental illness are overwhelming emergency departments. Other studies have found that a notable percentage of ED visits by Medicaid-covered adults is for care that could have been avoided through better physician management of chronic conditions, although estimates vary considerably. (20)

Policy Implications

Contrary to widespread perceptions that Medicaid enrollees frequently use emergency departments for routine care, the majority of ED visits by nonelderly Medicaid patients involve symptoms suggesting urgent or more serious medical problems. These findings also highlight two categories of conditions with the greatest potential to reduce ED utilization for both nonelderly Medicaid and privately insured populations if access to appropriate alternative care settings were available -- first, acute respiratory and other common infections in children, and second, injuries among all nonelderly individuals.

Diagnostic information supports the concept that patients seeking ED care for certain conditions could be treated in lower-cost environments, but primary care settings may not be a practical solution in every case. Many primary care practices are unable to see patients quickly enough to manage urgent problems or do not have the necessary equipment on site. Alternative care settings would need to deliver prompt care for urgent cases while having appropriate services and equipment to diagnose and treat less complex cases.

Effective management of easily treatable infections can require urinalysis or intravenous fluid administration for dehydration, and minor to moderate injuries may involve suturing, X-rays, and splinting. The capacity and location of alternative providers -- potentially urgent care centers, retail clinics, or others -- that can manage urgent problems at lower cost than emergency departments will ultimately determine how many patients can be redirected to more affordable settings.

State policy makers have been tackling high ED utilization among Medicaid enrollees through three broad strategies:

1) Raising copayments or denying payment for certain categories of ED visits determined after the fact to be medically unnecessary -- for example, chest pain symptoms that could indicate a heart attack but ultimately diagnosed as indigestion; (21)

2) Encouraging primary care providers to address high ED utilization through expanded access and improved chronic disease management; and

3) Increasing the participation of providers in lower-cost settings, such as urgent care centers, within health plan networks.

However, recent evidence indicates that copayments are ineffective at reducing nonurgent ED visits among Medicaid enrollees, (22) and such policies raise legitimate concerns that low-income patients with genuinely urgent health issues will forgo needed care. Furthermore, some hospitals actively seek to attract patients with minor problems to their emergency departments by advertising short wait times on billboards and through mobile phone applications. (23) Broader payment reforms -- such as accountable care organizations -- that shift away from fee-for-service payment could change the incentives for hospitals to market their EDs so aggressively while promoting greater investment in lower-cost settings equipped to address urgent medical needs.

Encouraging primary care providers to reduce high ED utilization through broader adoption of patient-centered medical home (PCMH) practices has the potential to decrease ED visits, though the evidence so far is mixed. (24) Some PCMH practices may help patients with chronic conditions better control symptoms and prevent complications, thereby reducing the need for emergency care.

Many PCMH initiatives also emphasize enhanced patient access to clinicians outside of standard business hours. However, growing pressures on the primary care workforce may constrain the effectiveness of PCMH initiatives in reducing ED volume. A substantial number of ED patients with a primary care physician report being referred to the ED by their doctor or having contacted their physician before seeking emergency care, suggesting that emergency departments already may be absorbing overflow from overburdened practices. (25) Primary care capacity was likely to be stretched even further in some states due to Medicaid and private insurance coverage expansions scheduled for 2014 under the federal health reform law.

Promoting the development of care settings beyond primary care that offer access to urgent services is also likely to be part of the solution for reducing ED utilization, although few would argue that such settings can replace primary care entirely. Urgent care and retail clinics have been shown to cost payers less per visit than emergency departments for conditions frequently treated in EDs, (26) partly because hospital EDs can levy a substantial facility fee. Moreover, many commercial health plan provider networks include retail clinics and urgent care centers, but there is not yet evidence of the overall cost-effectiveness of these approaches.

Retail clinics, commonly located in pharmacies or retail chains, are equipped to treat uncomplicated respiratory, eye, and ear infections and can perform rapid strep tests. Urgent care centers are able to treat a wider range of conditions and typically operate during evenings and weekends. Most urgent care centers have a physician, X-ray equipment, and intravenous administration capability on site, enabling them to address minor to moderately acute problems requiring urgent attention, including injuries such as lacerations and simple fractures. (27)

However, very little information exists about the participation of these providers in Medicaid programs. Only two out of 31 nonprofit Medicaid health plans surveyed in 2011 reported contracts with urgent care centers, (28) and retail clinics are often not situated in low-income neighborhoods, limiting their potential to improve access for the majority of Medicaid patients. (29)

Furthermore, just as many primary care physicians decline to participate in Medicaid due to low reimbursement rates and administrative burdens, urgent care centers and retail clinics may similarly choose not to participate. Low Medicaid participation rates among most providers likely means that meaningfully reducing the volume of Medicaid patient ED visits will require new payer incentives to engage a greater number and diversity of providers.

Ultimately, broader payment reform toward models that emphasize provider accountability for populations rather than fee-for-service payment may motivate providers to invest in alternative care settings where patients can receive timely treatment for urgent problems without needing to resort to emergency departments.

Sources and Further Reading

Notes

1. Chalfin, Donald B., et al., "Impact of Delayed Transfer of Critically Ill Patients from the Emergency Department to the Intensive Care Unit," Critical Care Medicine, Vol. 35, No. 6, (June 2007); National Quality Forum, National Voluntary Consensus Standards for Emergency Care -- Phase II: Hospital-based Emergency Care Measures, Washington, D.C. (June 2008); American College of Emergency Physicians, Definition of a Boarded Patient, Policy Statement, Dallas, Texas (January 2011).

2. DeLia, Derek, and Joel Cantor, Emergency Department Utilization and Capacity, Research Synthesis Report No. 17, Robert Wood Johnson Foundation, Princeton, N.J. (July 2009).

3. Ostrom, Carol M., "State Medicaid Program to Stop Paying for Unneeded ER Visits," The Seattle Times, (Feb. 7, 2012); Booth, Michael, "Medicaid Dispute Pits 'Shared Responsibility,' Care of Poor," The Denver Post, (Jan. 29, 2012); Trapp, Doug, "CMS Denies Florida's Bid to Raise Medicaid Cost-Sharing," American Medical News, (Feb. 24, 2012).

4. American College of Emergency Physicians, "Frequent Flyer Study Being Used to Perpetuate Myth That Emergency Room Overcrowding is Caused by Patients with Non-Urgent Conditions," News Release (April 2, 2009); Roser, Mary Ann, "Austin ER's Got 2,678 Visits from 9 People Over 6 Years: Task Force Seeking Ways to Divert Non-Emergencies Away from Emergency Rooms," The Statesman, (April 1, 2009).

5. Data on elderly patients are not presented because they frequently have multiple coverage sources, making comparisons by payment source less informative.

6. American College of Emergency Physicians, "Health Plans and State Medicaid Officials Deny Coverage of Emergency Care, Misapplying a Research Tool, Says Research Author," News Release (Feb. 27, 2012).

7. Because of insufficient sample sizes, triage acuity by payer source cannot be measured accurately.

8. Mehrotra, Ateev, et al., "Retail Clinics, Primary Care Physicians, and Emergency Departments: Comparison of Patients' Visits," Health Affairs, Vol. 27, No. 5 (September 2008).

9. Ku, Leighton, and Christine Ferguson, Medicaid Works: A Review of How Public Insurance Protects the Health and Finances of Children and Other Vulnerable Populations, The George Washington University, School of Public Health and Health Services, Washington, D.C. (June 2011).

10. U.S. Government Accountability Office (GAO), Medicaid and CHIP: Most Physicians Serve Covered Children but Have Difficulty Referring Them for Specialty Care, Pub. GAO-11-624, Washington, D.C. (June 2011).

11. Kaiser Family Foundation, Kaiser Commission on Medicaid and the Uninsured, Low-Income Adults Under Age 65 -- Many are Poor, Sick, and Uninsured, Policy Brief, Washington, D.C. (June 2009); Coughlin, Teresa A., Sharon K. Long and Yu-Chu Shen, "Assessing Access to Care Under Medicaid: Evidence for the Nation and Thirteen States," Health Affairs, Vol. 24, No. 4 (July 2005); Mortensen, Karoline and Paula H. Song, "Minding the Gap: A Decomposition of Emergency Department Use by Medicaid Enrollees and the Uninsured," Medical Care, Vol. 46, No. 10 (October 2008).

12. The percentage of patients seen in the ED with two or more chronic conditions is likely higher because this estimate does not count different conditions in the same diagnostic group, such as pregnancy and gestational diabetes. Also, physicians in emergency settings do not customarily record diagnoses for billing purposes that have no direct bearing on the reason for the visit.

13. Finlayson, Marcia L., and Elizabeth W. Peterson, "Falls, Aging and Disability," Physical Medicine and Rehabilitation Clinics of North America, Vol. 21, No. 2, (May 2010).

14. Cheung, Paul T., et al., "National Study of Barriers to Timely Primary Care and Emergency Department Utilization Among Medicaid Beneficiaries," Annals of Emergency Medicine, published online (March 14, 2012).

15. Authors' calculations using data from the Center for Studying Health System Change 2008 Health Tracking Physician Survey.

16. Lowe, Robert A., et al., "Association Between Primary Care Characteristics and Emergency Department Use in a Medicaid Managed Care Organization," Medical Care, Vol. 43, No. 8 (August 2005).

17. Authors' calculations using data from the Center for Studying Health System Change 2008 Health Tracking Physician Survey. Specialists excluded those working most hours on hospital staff or in emergency departments and physicians in primary care specialties.

18. Kaiser Permanente, Oakland, Calif., California Primary Care Association, Sacramento, Calif., and California Association of Public Hospitals and Health Systems, Oakland, Calif., Preliminary Findings: Specialty Care Access Survey (January 2008); California HealthCare Foundation, Understanding Common Reasons for Patient Referrals in Difficult-to-Access Specialties, Oakland, Calif. (May 2009).

19. Weiss, Anthony P., et al., "Patient and Practice-Related Determinants of Emergency Department Length of Stay for Patients with Psychiatric Illness," Annals of Emergency Medicine, published online (May 4, 2012).

20. Oster, Ady, and Andrew B. Bindman, "Emergency Department Visits for Ambulatory Care Sensitive Conditions," Medical Care, Vol. 41, No. 2 (February 2003); Choudhry, Lina, et al., The Impact of Community Health Centers and Community-Affiliated Health Plans on Emergency Department Use, Association for Community Affiliated Plans, Washington, D.C., and National Association of Community Health Centers, Bethesda, Md. (April 2007).

21. Ostrom (2012).

22. Mortensen, Karoline, "Copayments Did Not Reduce Medicaid Enrollees' Nonemergency Use of Emergency Departments," Health Affairs, Vol. 29, No. 9 (September 2010).

23. Christianson, Jon B., et al., Economic Downturn Strains Miami Health Care System, Community Report No. 11, Center for Studying Health System Change, Washington, D.C. (September 2011).

24. Peikes, Deborah, et al., Early Evidence on the Patient-Centered Medical Home, Agency for Healthcare Research and Quality, Rockville, Md. (February 2012).

25. Berry, Anne, et al., "Why Do Parents Bring Children to the Emergency Department for Nonurgent Conditions: A Qualitative Study," Academic Pediatrics, Vol. 8, No. 6 (November 2008); American College of Emergency Physicians, "Overburdened Primary Care Physicians Send Patients to the ER," News Release (Oct. 15, 2011).

26. Mehrotra, et al., (Sept. 1, 2009).

27. Weinick, Robin M., Rachel M. Burns and Ateev Mehrotra, "Many Emergency Department Visits Could be Managed at Urgent Care Centers and Retail Clinics," Health Affairs, Vol. 29, No. 9 (September 2010).

28. Association for Community Affiliated Plans, ACAP Fact Sheet: Ensuring Access Through Strong Provider Networks, Washington, D.C. (October 17, 2011).

29. Pollack, Craig E., and Katrina Armstrong, "Geographic Accessibility of Retail Clinics for Underserved Populations," Archives of Internal Medicine, Vol. 169, No. 10 (May 2009).

Data Source

This analysis draws on hospital emergency department (ED) visit data from the National Center for Health Statistics 2008 National Hospital Ambulatory Medical Care Survey Emergency Department (NHAMCS-ED) public use micro-data files. The 2008 NHAMCS-ED is a nationally representative probability sample of visits to the emergency departments of general and short-stay hospitals in the United States, excluding federal, military, and Veterans Administration hospitals. A national sample of hospitals was asked to provide data for a systematic random sample of patient visits during a randomly assigned four-week reporting period, utilizing clinical data from patient charts and hospital administrative records. The 2008 NHAMCS-ED includes 34,134 records from participating EDs. More details about the NHAMCS-ED are available on the Centers for Disease Control and Prevention website: http://www.cdc.gov/nchs/ahcd/about_ahcd.htm#NHAMCS.

NHAMCS-ED variables used in this analysis included expected source of payment, visit acuity, and provider diagnoses. Payment source was recoded for this study into private insurance, Medicaid/CHIP, Medicare, uninsured (self-pay, no charge/charity), or other/unknown (worker's compensation, other, missing, unknown). Visit acuity -- the immediacy with which a patient needs to be seen -- is based on the initial assessment of the patient upon arrival by a practitioner (e.g., triage nurse) and was classified into five categories: (1) emergent -- patient must be seen immediately or within 15 minutes of arrival; (2) urgent -- 15-60 minutes; (3) semi-urgent -- 1-2 hours; (4) nonurgent -- 2-24 hours; and (5) no triage or unknown. Primary diagnosis is based on the first of three diagnoses recorded for the visit by the principal medical provider, with some exceptions. Further detail about how diagnoses were coded for this study is provided in the Technical Appendix.

The denominators used to calculate visit rate estimates come from two sources. Private enrollment data were derived from the 2008 National Health Interview Survey. The count included individuals reporting private coverage only as well as those with private insurance plus additional coverage sources. Medicaid enrollment data are from the Medicaid Statistical Information System for fiscal year 2008. Medicaid enrollment represents the number of unique individuals -- Medicaid eligibles -- at any time during the fiscal year and is based on administrative data submitted by states to the Centers for Medicare and Medicaid Services.

Supplementary Table 1: ED Visit Rates per 100 Enrollees by Triage Acuity, Insurance Type, and Age Group, 2008

Children Ages 0-12: Emergent -- Medicaid 5.1, Private 3.3; Urgent -- Medicaid 16.6, Private 10.5; Semi-urgent -- Medicaid 9.3, Private 5.7; Nonurgent -- Medicaid 4.0, Private 1.8; No triage/unknown -- Medicaid 5.5, Private 3.5.

Teens/Young Adults Ages 13-20: Emergent -- Medicaid 6.2, Private 3.2; Urgent -- Medicaid 14.7, Private 8.3; Semi-urgent -- Medicaid 8.7, Private 4.5; Nonurgent -- Medicaid 4.3, Private 1.4; No triage/unknown -- Medicaid 5.7, Private 3.1.

Adults Ages 21-64: Emergent -- Medicaid 10.0, Private 4.6; Urgent -- Medicaid 20.8, Private 9.1; Semi-urgent -- Medicaid 12.4, Private 5.4; Nonurgent -- Medicaid 5.3, Private 1.4; No triage/unknown -- Medicaid 6.8, Private 2.4.

Source: Center for Studying Health System Change analysis of 2008 NHAMCS; MSIS FY 2008; NHIS 2008.

Technical Appendix

Emergency Department Data

The emergency department visit data used in this analysis are from the 2008 National Hospital Ambulatory Medical Care Survey of Emergency Departments (NHAMCS-ED). Administered by the Centers for Disease Control and Prevention, National Center for Health Statistics (NCHS), the 2008 survey comprises a nationally representative probability sample of visits to emergency departments of noninstitutional general and short-stay hospitals across the 50 states and the District of Columbia. Additional information about the survey is available at www.cdc.gov/nchs/ahcd.htm.

The 2008 dataset includes 34,134 sampled visits, representing approximately 123.7 million total emergency department visits. This analysis focuses on ED visits by individuals aged 0 to 64 and includes 7,932 visits with Medicaid as the primary expected payment source and 10,548 visits with private insurance as the primary expected payment source. Data analyses were conducted using SUDAAN statistical software to produce standard errors accounting for the complex survey design.

The survey instrument is a patient record form (PRF). Trained hospital staff completed a PRF following each visit to document key elements of the encounter. Key variables used in this analysis include provider diagnoses, whether the visit was injury-related, expected source of payment, and visit acuity.

Provider's diagnosis. The primary diagnosis and symptoms associated with the patient's most important reason for the visit and up to two other significant diagnoses were recorded on the PRF. These represent the final diagnoses related to the visit according to the principal physician's best judgment at the time of the visit. Textual descriptions of the diagnoses were coded according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM).

Injury. Hospital staff recorded whether each visit was related to an injury, poisoning, or adverse medical event, along with the patient's verbatim description of the circumstances leading to the injury. Verbatim responses were converted by NCHS medical coders into (up to three) external cause of injury codes according to the ICD-9-CM Supplementary Classification of External Causes of Injury and Poisoning Codes (E-codes). Visits were classified as injuries if the injury checkbox on the patient record form was coded as "yes," if any external cause of injury was reported, if any of the three reasons for the visit as reported by the patient were classified as an injury, or if any of the three diagnosis codes fell into the injury or poisoning chapter of the ICD-9-CM.

Payment source. Trained hospital staff consulted patients' files or billing records and marked the expected payment source or sources for a given visit by checking the appropriate boxes on the PRF. Payment sources included private insurance, Medicare, Medicaid/Children's Health Insurance Program (CHIP), worker's compensation, self-pay, no charge/charity, other, or unknown. The PRF allowed for recording of multiple payment sources, and the NHAMCS data file included an indicator variable for each source. For this study, a primary expected source of payment was constructed by applying the following hierarchy: Medicare, Medicaid/CHIP, private insurance, worker's compensation, self-pay, no charge, other, unknown. (Technical Note 1) Consequently, visits with expected payment from both Medicare and Medicaid are assigned to Medicare, which is typically the primary source of payment for emergency services for dually eligible enrollees.

Visit acuity. Visit acuity -- the immediacy with which a patient needs to be seen -- is based on the initial assessment of the patient upon arrival at the ED by a practitioner (e.g., triage nurse) and is expressed in minutes or hours. Visit acuity was classified for this analysis into five categories: (1) emergent -- patient needs to be seen immediately or within 15 minutes of arrival; (2) urgent -- 15-60 minutes; (3) semi-urgent -- 1-2 hours; (4) nonurgent -- 2-24 hours; and (5) no triage or unknown triage.

The urgency of the visit was unknown in approximately 15 percent of ED visits in the 2008 NHAMCS data, because some emergency departments do not maintain records of triage decisions and some triage decisions were not documented. The same proportion of Medicaid and private visits have unknown urgency.

Primary condition. The injury indicator and diagnosis codes were used in this analysis to construct a categorical variable summarizing the patient's primary condition related to the visit. Non-injury visits were then classified hierarchically indicating presence of a major physical or mental disability or pregnancy, using all three diagnosis fields. These indicators served as proxy measures for serious comorbidities in the population using ED services that could help explain higher ED utilization by the Medicaid population. The disabling conditions were based on a list of more than 240 ICD-9-CM diagnosis codes considered to indicate a disability, as developed in earlier research (e.g., cerebral palsy). (Technical Note 2) Remaining visits were grouped into major diagnostic categories (MDCs) -- an ICD-9-CM classification system that divides diagnoses into mutually exclusive categories based on the associated organ system or related specialty of the principal diagnosis -- according to the first ICD-9 code listed for that visit that was not a symptom or procedure. In the final analysis, visits related to viral conditions were separated from MDC categories and estimated independently because of the high percentage of visits related to this group of common conditions. This category was assigned based on the presence of specific diagnoses in any of the three diagnosis fields and was applied hierarchically after pregnancy. See Technical Appendix Table 1 for a complete summary of the diagnostic groupings. (Technical Note 3)

Private Insurance and Medicaid Enrollment Data

The denominators used to compute visit rate estimates come from two sources. Private enrollment data were obtained from the 2008 National Health Interview Survey (NHIS), which is the source customarily used alongside NHAMCS data. The count included individuals reporting private coverage only as well as those with private insurance and additional coverage sources. Private enrollment estimates and standard errors for the specific age ranges used in this study were provided to the authors by NCHS staff.

Medicaid enrollment data are from the Medicaid Statistical Information System (MSIS) Summary File for fiscal year 2008. Medicaid enrollment equals the number of unique individuals eligible for Medicaid coverage at any time during the fiscal year and is based on administrative data submitted by states to the Centers for Medicare and Medicaid Services (CMS). The authors used MSIS data rather than NHIS data to construct denominators for Medicaid visit rates for two reasons. The NHIS records respondents' insurance status at the time of interview and therefore does not count enrollees who were not covered by Medicaid at the time of the interview but were enrolled in other months. People covered for only part of the year represent a significant minority of all Medicaid enrollees. According to the MSIS, 43.2 million people aged 0-64 were enrolled in Medicaid in June 2008, while the total number of unique eligibles for fiscal year 2008 was 54.7 million people. In contrast, estimated Medicaid enrollment in 2008 for this age group was only 34.5 million according to the NHIS. Evidence suggests that NHIS data may not adequately measure Medicaid enrollment for the purpose of this study. Analysis of 2002 NHIS data linked to administrative MSIS data found that the survey undercounted the number of Medicaid enrollees by nearly 22 percent. (Technical Note 4) The same study also found that among survey respondents who were matched to the MSIS database at the time of the interview, 32 percent incorrectly reported having no Medicaid coverage. To avoid undercounting, this study used MSIS data to more accurately capture the number of people enrolled in Medicaid at any time during the year. (Technical Note 5)

The nature of the NHAMCS data also factored into the decision to use MSIS enrollment data. Emergency department visits in the NHAMCS are sampled from hospital administrative records, which include visits by individuals who fall outside the scope of the NHIS sampling frame (such as institutionalized and homeless people). Thus, a denominator based on administrative data is a more appropriate choice for this study given the administrative source underlying the numerator.

To demonstrate the impact of using administrative versus survey data for enrollment counts, emergency department visit rates per 100 Medicaid enrollees were calculated using both NHIS and MSIS data. The Medicaid visit rate for adults aged 21-64 was 72.4 visits per 100 enrollees using NHIS data and 45.8 visits per 100 enrollees using MSIS data. Thus, using the administrative source narrows the difference in visit rates between Medicaid and private insurance by 27 visits per enrollee (or roughly 55 percent). This method does not, however, change the distribution of visits by source of payment (i.e., percentage of visits that are nonurgent), because these estimates do not depend on the size of enrollment. As a result, visit rates for Medicaid enrollees in this study are lower than previously published rates but are believed by the authors to be more accurate.

Technical Appendix Notes

Technical Note 1. The current version of the 2008 NHAMCS data file includes a constructed summary variable, PAYTYPER, with the same hierarchical assignment used in this study. However, at the time data analysis for this study was performed, a different summary variable was present in the data -- PAYTYPE -- that employed a slightly different hierarchy and did not match the definition used in previous years of the survey. Consequently, the authors constructed their own hierarchy, as described.

Technical Note 2. Ozminkowski, Ronald J., et al., Private Payers Serving Individuals with Disabilities and Chronic Conditions, The MEDSTAT Group, U.S. Department of Health and Human Services (January 2000). See Appendix Tables A-1 and A-3 for lists of diagnosis codes associated with potentially disabling physical conditions for adults. These lists were modified slightly by the authors according to clinical input from an emergency department physician. The modified list is available from the authors on request.

Technical Note 3. Note that the multi-stage process defining PRIMCOND prioritizes injuries and then disabling conditions, pregnancy, and viral conditions over other diagnosis categories -- i.e., the presence of these diagnoses in any of the three diagnosis fields supersedes all other diagnoses. For example, if the primary diagnosis (DIAG1) for a non-injury visit is a skin condition, while the second diagnosis (DIAG2) is pregnancy related, the visit will be classified as PRIMCOND=2 (pregnancy).

Technical Note 4. State Health Access Data Assistance Center, Phase IV Research Results: Estimating the Medicaid Undercount in the National Health Interview Survey (NHIS) and Comparing False-Negative Medicaid Reporting in NHIS to the Current Population Survey (CPS).

Technical Note 5. The MSIS Medicaid enrollment counts included people dually eligible for Medicare and Medicaid coverage, even though ED use by dual eligibles is typically covered by Medicare. The result is a visit rate that reflects each program's obligation for its population. The inclusion of this population makes little difference for children aged 0-12 and teens/young adults aged 13-20, where dual eligibles comprise 0.1 percent or fewer of Medicaid enrollees. Dual eligibles account for 16.3 percent of Medicaid enrollees aged 21-64 and about 6.5 percent of total Medicaid enrollment among people aged 0 to 64.

Funding Acknowledgement

This research was supported by the Robert Wood Johnson Foundation.