Research

Publications

Our team is engaged in a wide range of research areas addressing critical questions in healthcare. Explore our publications by category below, or view the full list here.

Charges and Reimbursements

Emergency departments are a critical part of the nation’s healthcare infrastructure, but their financial stability is increasingly threatened by persistent pressures. These studies analyze trends, variations, and disparities in healthcare charges, payments, and reimbursements across payer groups, services, and patient demographics, with a focus on emergency care and hospital-based procedures.

  1. Wang Y, Liu V, Wang Y, Bai G, Hsia RY. Emergency Department Trauma Activation Fees by Payer Type. JAMA Surg. Published online April 17, 2024.
  2. Burke LG, Wild RC, Orav EJ, Hsia RY. Are Trends in Billing for High-Intensity Emergency Care Explained by Changes in Services Provided in the Emergency Department? An Observational Study Among US Medicare Beneficiaries. BMJ Open. 2018;8(1):e019357.
  3. Valdovinos E, Le S, Hsia RY. In California, Not-For-Profit Hospitals Spent More Operating Expenses On Charity Care Than For-Profit Hospitals Spent. Health Aff. 2015; 34(8):1296-1303.
  4. Fox JP, Tyle JA, Vashi AA, Hsia RY, Saxe JM. Variation in the value of colectomy for cancer across hospitals: mortality, readmissions, and costs. Surgery. 2014; 156(4): 849-860.
  5. Wang T, Srebotnjak T, Brownell J, Hsia RY. Emergency department charges for asthma-related outpatient visits by insurance status. J Health Care Poor Underserved. 2014; 25(1):396-405.
  6. Hsia RY, Antwi YA, Weber E. Analysis of Variation in Charges and Prices Paid for Vaginal and Caesarean Section births: A Cross-Sectional Study. BMJ Open. 2014; 4:e004017. 
  7. Hsia RY, Antwi YA, Brownell JP. Variation in Charges for Ten Common Blood Tests in California Hospitals: A Cross-Sectional Analysis. BMJ Open. 2014; 4(8):e005482.
  8. Hsia RY, Antwi YA, Weber E, Brownell JP. A cross-sectional analysis of variation in charges and prices across California for percutaneous coronary intervention. PLoS One. 2014; 9(8):e103829.
  9. Hsia RY, Antwi YA. Variation in Charges for Emergency Department Visits Across California. Ann Emerg Med. 2014; 64(2):120-126.e4.
  10. Caldwell N, Srebotnjak T, Wang T, Hsia RY. “How Much Will I Get Charged for This?” Patient Charges for Top Ten Diagnoses in the Emergency Department. PLoS One. 2013;8(2):e55491.
  11. Hsia RY, Kothari AH, Srebotnjak T, Maselli J. Health Care as a “Market Good”? Appendicitis as a Case Study. Arch Intern Med. 2012; 172(10):818-819.
  12. Hsia RY, MacIsaac D, Palm E, Baker LC. Trends in charges and payments for non-hospitalized emergency department pediatric visits, 1996-2003. Acad Emerg Med. 2008; 15(4):347-354.
  13. Hsia RY, MacIsaac D, Baker LC. Decreasing Reimbursements for Outpatient ED Visits Across Payer Groups from 1996-2004. Ann Emerg Med. 2008; 51(3):265-274. 
Closures and Their Effects on Patient Outcomes

This research focuses on the trends, risk factors, and disparities associated with the closure and availability of emergency departments (EDs) and trauma centers in the United States. This body of work examines how financial pressures, community characteristics, and healthcare policies contribute to closures, and explores impacts on patient access, treatment outcomes, mortality rates, and system-level disparities, particularly for historically underserved populations and those in underserved areas.

  1. Hsia RY, Shen YC. Emergency Department Closures And Openings: Spillover Effects On Patient Outcomes In Bystander Hospitals. Health Affairs. 2019; 38(9): 1496-1504.
  2. Hsuan C, Hsia RY, Horwitz J, Ponce NA, Rice T, Needleman J. Ambulance Diversions Following Public Hospital Emergency Department Closures. Health Serv Res. 2019; 00:1-10. doi.org/10.1111/1475-6773.13147.
  3. Chow JL, Niedzwiecki MJ, Hsia RY. Trends in the Supply of California’s Emergency Departments and Inpatient Services, 2005-2014: A Retrospective Analysis. BMJ Open. 2017;7(5):e014721.
  4. Shen YC, Hsia RY. Geographical Distribution of Emergency Department Closures and Consequences on Heart Attack Patients. Working Paper (No. 22861). National Bureau of Economics Research, November 2016.
  5. Shen YC, Hsia RY. Association Between Emergency Department Closure and Treatment, Access, and Health Outcomes Among Patients with Acute Myocardial Infarction. Circulation. 2016;134(20):1597-1599.
  6. Crandall M, Sharp D, Wei X, Nathens A, Hsia RY. Effects of Closure of an Urban Level 1 Trauma Centre on Adjacent Hospitals and Local Injury Mortality: A Retrospective, Observational Study. BMJ Open. 2016; 6(5):e011700.
  7. Li S, Dor A, Pines JM, Zocchi MS, Hsia RY. The Relationship of Financial Pressures and Community Characteristics to Closure of Private Safety Net Clinics. Med Care Res Rev. 2015. doi:10.1177/1077558715622897
  8. Liu C, Srebotnjak T, Hsia RY. Emergency Department Closures Are Associated With Increased Inpatient Mortality At Nearby Hospitals. Health Aff (Millwood). 2014; 33(8):1323-1329.
  9. Hsia RY, Srebotnjak T, Maselli J, Crandall M, McCulloch C, Kellermann AL. The Association of Trauma Center Closures with Increased Inpatient Mortality for Injured Patients. J Trauma Acute Care Surg. 2014; 76(4):1048-1054.
  10. Hsia RY, Kanzaria HK, Srebotnjak T, Maselli J, McCulloch C, Auerbach AD. Is emergency department closure resulting in increased distance to the nearest emergency department associated with increased inpatient mortality? Ann Emerg Med. 2012; 60(6):707-715.
  11. Shen YC, Hsia RY. Does Decreased Access to Emergency Departments Affect Patient Outcomes? Analysis of AMI Population 1996-2005. Health Serv Res. 2012; 47(1):188-210.
  12. Hsia RY, Srebotnjak T, Kanzaria HK, McCulloch C, Auerbach AD. System-level health disparities in California emergency departments: minorities and Medicaid patients are at higher risk of losing their emergency departments. Ann Emerg Med. 2012; 59:358-365.
  13. Hsia RY, Kellermann A, Shen YC. Factors Associated With Closure of Emergency Departments in the United States. JAMA. 2011; 305(19):1978-1985. 
  14. Hsia RY, Shen YC. Rising Closures of Trauma Centers Disproportionately Burdens Vulnerable Populations. Health Aff (Millwood). 2011; 30(10):1912-1920. 
  15. Shen YC, Hsia RY, Kuzma K. Understanding the Risk Factors of Trauma Center Closures: Do Financial Pressure and Community Characteristics Matter? Med Care. 2009; 47(9):968-978.
Department of Health Care Access and Information (HCAI)

The following studies use California healthcare data from the Department of Healthcare Access and Information (HCAI). 

  1. Hsia RY, Wang NE, Torres H, Saynina O, Wise PH. Disparities in trauma center access despite increasing utilization: data from California, 1999-2006. J Trauma Acute Care Surg. 2010;68(1):217-224.
  2. Hsia RY, Wang E, Saynina O, Wise P, Perez-Stable EJ, Auerbach A. Factors associated with trauma center use for elderly patients with trauma: a statewide analysis, 1999-2008. Arch Surg. 2011;146(5):585-592.
  3. Shen YC, Hsia RY. Does decreased access to emergency departments affect patient outcomes? Analysis of acute myocardial infarction population 1996-2005. Health Serv Res. 2012;47(1pt1):188-210.
  4. Hsia RY, Kothari AH, Srebotnjak T, Maselli J. Health care as a “market good”? Appendicitis as a case study. Arch Intern Med. 2012;172(10):818-819.
  5. Hsia RY, Srebotnjak T, Kanzaria HK, McCulloch C, Auerbach AD. System-level health disparities in California emergency departments: minorities and Medicaid patients are at higher risk of losing their emergency departments. Ann Emerg Med. 2012;59(5):358-365.
  6. Hsia RY, Kanzaria HK, Srebotnjak T, Maselli J, McCulloch C, Auerbach AD. Is emergency department closure resulting in increased distance to the nearest emergency department associated with increased inpatient mortality? Ann Emerg Med. 2012;60(6):707-715.e4.
  7. Hsia RY, Asch SM, Weiss RE, et al. California hospitals serving large minority populations were more likely than others to employ ambulance diversion. Health Aff (Millwood). 2012;31(8):1767-1776.
  8. Hsia RY, Brownell J, Wilson S, Gordon N, Baker LC. Trends in adult emergency department visits in California by insurance status, 2005-2010. JAMA. 2013;310(11):1181-1183.
  9. Sun BC, Hsia RY, Weiss RE, et al. Effect of emergency department crowding on outcomes of admitted patients. Ann Emerg Med. 2013;61(6):605-611.e6.
  10. Gabayan GZ, Asch SM, Hsia RY, Zingmond D, et al. Factors associated with short-term bounce-back admissions after emergency department discharge. Ann Emerg Med. 2013;62(2):136-144.e1.
  11. Hsia RY, Asch SM, Weiss RE, et al. Is emergency department crowding associated with increased "bounceback" admissions? Med Care. 2013;51(11):1008-1014.
  12. Sun BC, Hsia RY, Weiss RE, et al. Effect of emergency department crowding on outcomes of admitted patients. Ann Emerg Med. 2013;61(6):605-611.e6.
  13. Hsia RY, Antwi YA, Weber E. Analysis of variation in charges and prices paid for vaginal and caesarean section births: a cross-sectional study. BMJ Open. 2014;4(1):e004017.
  14. Hsia RY, Srebotnjak T, Maselli J, Crandall M, McCulloch C, Kellermann AL. The association of trauma center closures with increased inpatient mortality for injured patients. J Trauma Acute Care Surg. 2014;76(4):1048-1054.
  15. Staudenmayer K, Lin F, Mackersie R, Spain D, Hsia RY. Variability in California triage from 2005 to 2009: a population-based longitudinal study of severely injured patients. J Trauma Acute Care Surg. 2014;76(4):1041-1047.
  16. Hsia RY, Antwi YA. Variation in charges for emergency department visits across California. Ann Emerg Med. 2014;64(2):120-126.e1-4.
  17. Hsia RY, Antwi YA, Weber E, Nath JB. A cross-sectional analysis of variation in charges and prices across California for percutaneous coronary intervention. PLoS One. 2014;9(8):e103829.
  18. Hsia RY, Antwi YA, Nath JB. Variation in charges for 10 common blood tests in California hospitals: a cross-sectional analysis. BMJ Open. 2014;4(8):e005482.
  19. Fox JP, Tyler JA, Vashi AA, Hsia RY, Saxe JM. A variation in the value of colectomy for cancer across hospitals: mortality, readmissions, and costs. Surgery. 2014 Oct;156(4):849-856,60.
  20. Liu C, Srebotnjak T, Hsia RY. California emergency department closures are associated with increased inpatient mortality at nearby hospitals. Health Aff (Millwood). 2014;33(8):1323-1329.
  21. Baker LC, Hsia RY. The association between community-level insurance coverage and emergency department use. Med Care. 2014;52(6):535-540.
  22. Hsia RY, Nath JB, Baker LC. Emergency department visits by children, adolescents, and young adults in California by insurance status, 2005-2010. JAMA. 2014;312(15):1587-1588.
  23. Choi JC, Hsia RY, Kim AS. Regional availability of mechanical embolectomy for acute ischemic stroke in California, 2009 to 2010. Stroke. 2015;46(3):762-768.
  24. Hsia RY, Nath JB, Baker LC. California emergency department visit rates for medical conditions increased while visit rates for injuries fell, 2005-11. Health Aff (Millwood). 2015;34(4):621-626.
  25. Zocchi MS, Hsia RY, Carr BG, Sarani B, Pines JM. Comparison of mortality and costs at trauma and non-trauma centers for minor and moderately severe injuries in California. Ann Emerg Med. 2016;67(1):56-67.e5.
  26. Staudenmayer K, Wang NE, Weiser TG, Maggio P, Mackersie RC, Spain D, Hsia RY. The triage of injured patients: mechanism of injury, regardless of injury severity, determines hospital destination. Am Surg. 2016;82(4):356-361.
  27. Crandall M, Sharp D, Wei X, Nathens A, Hsia RY. Effects of closure of an urban level 1 trauma centre on adjacent hospitals and local injury mortality: a retrospective, observational study. BMJ Open. 2016;6(5):e011700.
  28. Hernandez-Boussard T, Morrison D, Goldstein BA, Hsia RY. Relationship of Affordable Care Act implementation to emergency department utilization among young adults. Ann Emerg Med. 2016;67(6):714-720.e1.
  29. Nath JB, Costigan S, Lin F, Vittinghoff E, Hsia RY. Federally qualified health center access and emergency department use among children. Pediatrics. 2016;138(4):e20160479.
  30. Chow JL, Niedzwiecki MJ, Hsia RY. Trends in the supply of California’s emergency departments and inpatient services, 2005-2014: a retrospective analysis. BMJ Open. 2017;7(5):e014721.
  31. Hsia RY, Sarkar N, Shen YC. Impact of ambulance diversion: Black patients with acute myocardial infarction had higher mortality than whites. Health Aff (Millwood). 2017;36(6):1070-1077.
  32. Kanzaria HK, Niedzwiecki MJ, Montoy JC, Raven MC, Hsia RY. Persistent frequent emergency department use: core group exhibits extreme levels of use for more than a decade. Health Aff (Millwood). 2017;36(10):1720-1728.
  33. McConville S, Raven MC, Sabbagh SH, Hsia RY. Frequent emergency department users: a statewide comparison before and after affordable care act implementation. Health Aff (Millwood). 2018;37(6):881-889.
  34. McConville S, Mooney AC, Williams BA, Hsia RY. How do ED patients with criminal justice contact compare with other ED users? A retrospective analysis of ED visits in California. BMJ Open. 2018;8(6):e020897.
  35. Hsia RY, Sarkar N, Shen YC. Is inpatient volume or emergency department crowding a greater driver of ambulance diversion? Health Aff (Millwood). 2018;37(7):1115-1122.
  36. Mooney AC, McConville S, Rappaport AJ, Hsia RY. Association of legal intervention injuries with race and ethnicity among patients treated in emergency departments in California. JAMA Netw Open. 2018;1(5):e182150.
  37. Kaiser SV, Lam R, Joseph GB, McCulloch C, Hsia RY, Cabana MD, et al. Limitations of using pediatric respiratory illness readmissions to compare hospital performance. J Hosp Med. 2018;13(11):737-742.
  38. Supat B, Brennan JJ, Vilke GM, Ishimine P, Hsia RY, Castillo EM. Characterizing pediatric high frequency users of California emergency departments. Am J Emerg Med. 2019;37(9):1699-1704.
  39. Hsia RY, Sabbagh SH, Guo J, Nuckton TJ, Niedzwiecki MJ. Trends in the utilisation of emergency departments in California, 2005-2015: a retrospective analysis. BMJ Open. 2018;8(7):e021392.
  40. Hsia RY, Markowitz AJ, Lin F, Guo J, Madhok DY, Manley GT. Ten-year trends in traumatic brain injury: a retrospective cohort study of California emergency department and hospital revisits and readmissions. BMJ Open. 2018;8(12):e022297.
  41. Niedzwiecki MJ, Kanzaria HK, Montoy JC, Hsia RY, Raven MC. Past frequent emergency department use predicts mortality. Health Aff (Millwood). 2019;38(1):155-158.
  42. Nath JB, Costigan S, Lin F, Vittinghoff E, Hsia RY. Access to federally qualified health centers and emergency department use among uninsured and Medicaid-insured adults: California, 2005 to 2013. Acad Emerg Med. 2019;26(2):129-139.
  43. Castillo EM, Brennan JJ, Howard J, Hsia RY, Chalmers C, et al. Factors associated with geriatric frequent users of emergency departments. Ann Emerg Med. 2019;74(2):270-275.
  44. Wei R, Mann NC, Dai M, Hsia RY. Injury-based geographic access to trauma centers. Acad Emerg Med. 2019;26(2):192-204.
  45. Hsia RY, Mannix RC, Guo J, et al. Revisits, readmissions, and outcomes for pediatric traumatic brain injury in California, 2005-2014. PLoS One. 2020;15(1):e0227981.
  46. Valdovinos EM, Niedzwiecki MJ, Guo J, Hsia RY. Effects of Medicaid expansion on access, treatment and outcomes for patients with acute myocardial infarction. PLoS One. 2020;15(4):e0232097.
  47. Valdovinos EM, Niedzwiecki MJ, Guo J, Hsia RY. The association of Medicaid expansion and racial/ethnic inequities in access, treatment, and outcomes for patients with acute myocardial infarction. PLoS One. 2020;15(11):e0241785.
  48. Zachrison KS, Li S, Reeves MJ, Adeoye O, Camargo CA, Schwamm LH, Hsia RY. Strategy for reliable identification of ischemic stroke, thrombolytics, and thrombectomy in large administrative databases. Stroke and Vascular Neurology 2021;6.
  49. Hsia RY, Krumholz HM, Shen YC. Evaluation of STEMI regionalization on access, treatment, and outcomes among adults living in nonminority and minority communities. JAMA Netw Open. 2020;3(11):e2025874.
  50. Shen YC, Hsia RY. Differential benefits of cardiac care regionalization based on driving time to percutaneous coronary intervention. Acad Emerg Med, 28: 519-529. 
  51. Montoy JCC, Shen YC, Brindis RG, Krumholz HM, Hsia RY. The impact of ST-segment elevation myocardial infarction (STEMI) regionalization programs on the treatment and outcomes of patients diagnosed with non-STEMI. J Am Heart Assoc. 2021;10(3):e016932. Epub 2021 Jan 20.
  52. Hsia RY, Shen YC, Krumholz H. Association of cardiac care regionalization with access, treatment, and mortality among patients with ST-elevation myocardial infarction. Circ Cardiovasc Qual Outcomes. 2021;14(3):e007195. Epub 2021 Mar 1.
  53. Ward MJ, Nikpay S, Shermeyer A, Nallamothu BK, Rokos I, Self WH, & Hsia RY. Interfacility Transfer of Uninsured vs Insured Patients With ST-Segment Elevation Myocardial Infarction in California. JAMA Network Open. 2023;6(6):e2317831
  54. Hsia RY, Zagorov S, Sarkar N, Savides MT, Feldmeier M, Addo N. Patterns in Patient Encounters and Emergency Department Capacity in California, 2011-2021. JAMA Netw Open. 2023;6(6):e2319438.
  55. Shen Y, Sarkar N, Hsia RY. Differential Treatment and Outcomes for Patients With Heart Attacks in Advantaged and Disadvantaged Communities. Journal of the American Heart Association. 0(0):e030506.
  56. Zachrison KS, Hsia RY, Schwamm LH, et al. Insurance-Based Disparities in Stroke Center Access in California: A Network Science Approach. Circ Cardiovasc Qual Outcomes. 2023;16(10):e009868. 
  57. Lin S, Shermeyer A, Nikpay S, Hsia RY, Ward MJ. Initial Treatment of Uninsured Patients with ST-Elevation Myocardial Infarction by Facility PCI Capabilities. Acad Emerg Med. 2024;31(2):119-128.
  58. Ruxin T, Feldmeier M, Addo N, Hsia RY. Trends by Acuity for Emergency Department Visits and Hospital Admissions in California, 2012 to 2022. JAMA Netw Open. 2023;6(12):e2348053. 
  59. Kim D, Huang D, Cogill S, Hsia RY, Yang S. Development and External Validation of a Pretrained Deep Learning Model for the Prediction of Non-Accidental Trauma Npj Digit Med. 2023;6(1):1-9.
Disparities in Access to Emergency Care

Uneven distribution of the supply of healthcare services often disproportionately affects historically marginalized and traditionally underserved populations, including low-income, rural, and minoritized populations. This research investigates disparities in emergency and trauma care access, treatment, and outcomes by focusing on structural inequities and healthcare facility availability.

  1. Shen YC, Feldmeier M, Hsia RY. Non–ST‐Segment–Elevation Myocardial Infarction and ST‐Segment–Elevation Myocardial Infarction Outcomes After a Percutaneous Coronary Intervention–Capable Facility Opening by Patient Race and Community Segregation. Journal of the American Heart Association. 2024;13(22):e035853.
  2. Hsia RY, Sarkar N, Shen YC. Provision of Stroke Care Services by Community Disadvantage Status in the US, 2009-2022. JAMA Netw Open. 2024;7(7):e2421010.
  3. Hsia RY, Shen YC. Structural Inequities In The Adoption Of Percutaneous Coronary Intervention Services By US Hospitals, 2000–20. Health Aff (Millwood). 2024;43(7):1011-1020.
  4. Shen YC, Sarkar N, Hsia RY. Differential Treatment and Outcomes for Patients With Heart Attacks in Advantaged and Disadvantaged Communities. Journal of the American Heart Association. 2023;12(17):e030506.
  5. Ward, M. J., Nikpay, S., Shermeyer, A., Nallamothu, B. K., Rokos, I., Self, W. H., & Hsia, R. Y. (2023). Interfacility Transfer of Uninsured vs Insured Patients With ST-Segment Elevation Myocardial Infarction in California. JAMA Network Open, 6(6), e2317831.
  6. Shen YC, Krumholz HM, Hsia RY. Do PCI Facility Openings and Closures Affect AMI Outcomes Differently in High- vs Average-Capacity Markets? JACC Cardiovasc Interv. 2023;16(10):1129-1140. 
  7. Wang C, Lindquist K, Krumholz H, Hsia RY. Trends in the likelihood of receiving percutaneous coronary intervention in a low-volume hospital and disparities by sociodemographic communities. PLoS One. 2023;18(1):e0279905. eCollection 2023.
  8. Montoy JCC, Shen YC, Hsia RY. Trends in inequities in the treatment of and outcomes for women and minorities with myocardial infarction. Annals of Emergency Medicine. 2022 Aug;80(2):108-117. Epub 2022 Jun 21.
  9. Shen YC, Sarkar N, Hsia RY. Structural inequities for historically underserved communities in the adoption of stroke certification in the United States. JAMA Neurology. 2022;79(8):777-786. Online ahead of print.
  10. Baehr A, Fought AJ, Hsia RY, Wiler JL, Ginde AA. The association between area deprivation index and emergency department discharge rates and revisits. Academic Emergency Medicine. 2022. doi:10.1111/acem.14486
  11. Hsia RY, Krumholz H, Shen Y-C. Evaluations of STEMI Regionalization on Access, Treatment, and Outcomes Among Adults Living in Nonminority and Minority Communities. JAMA Netw Open. 2020;3(11):e2025874. 
  12. Valdovinos EM, Niedzwiecki MJ, Guo, J, Hsia RY. The association of Medicaid expansion and racial/ethnic inequities in access, treatment, and outcomes for patients with acute myocardial infarction. PLOS ONE. 2020;15(11):e0241785. 
  13. Valdovinos EM, Niedzwiecki MJ, Guo J, Hsia RY. Effects of Medicaid Expansion on Access, Treatment and Outcomes for Patients With Acute Myocardial Infarction. PLoS ONE. 2020;15(4):e0232097.
  14. Hsuan C, Hsia RY, Horwitz J, Ponce NA, Rice T, Needleman J. Ambulance Diversions Following Public Hospital Emergency Department Closures. Health Serv Res. 2019; 00:1-10. doi.org/10.1111/1475-6773.13147.
  15. Nath JB, Costigan S, Lin F, Vittinghoff E, Hsia RY. Access to Federally Qualified Health Centers and Emergency Department Use Among Uninsured and Medicaid-insured Adults: California, 2005 to 2013. Acad Emerg Med. 2019; doi: 10.1111/acem.13494.
  16. Niedzwiecki MJ, Kanzaria HK, Montoy JC, Hsia RY, Raven MC. Past Frequent Emergency Department Use Predicts Mortality. Health Aff (Millwood). 2019;38(1):155-158.
  17. Hsia RY, Huang D, Mann NC, Colwell C, Mercer MP, Dai M, Niedzwiecki MJ. A US National Study of the Association Between Income and Ambulance Response Time in Cardiac Arrest. JAMA Netw Open. 2018;1(7):e185202.
  18. Niedzwiecki MJ, Sharma P, Kanzaria HK, McConville S, Hsia RY. Factors Associated With Emergency Department Use by Patients With and Without Mental Health Diagnoses. JAMA Netw Open. 2018;1(6);e183528.
  19. Mooney AC, McConville S, Rappaport AJ, Hsia RY. Association of Legal Intervention Injuries with Race and Ethnicity Among Patients Treated in Emergency Departments in California. JAMA Netw Open. 2018;1(5):e182150.
  20. McConville S, Mooney AC, Williams BA, Hsia RY. How Do ED Patients with Criminal Justice Contact Compare to Other ED Users? A Retrospective Analysis of ED Visits in California. BMJ Open. 2018;8:e020897.
  21. Niedzwiecki MJ, Hsia RY, Shen YC. Not All Insurance Is Equal: Differential Treatment and Health Outcomes by Insurance Coverage Among Nonelderly Adult Patients With Heart Attack. J Am Heart Assoc. 2018;7(11):e008152.
  22. McConville S, Raven MC, Sabbagh SH, Hsia RY. Frequent Emergency Department Users: A Statewide Comparison Before and After Affordable Care Act Implementation. Health Aff (Millwood). 2018;37(6):881-889.
  23. Rothman A, McConville S, Hsia RY, Metzger L, Ahalt C, Williams BA. Differences Between Incarcerated and Non-Incarcerated Patients Who Die in Community Hospitals Highlight the Need for Palliative Care Services for Seriously Ill Prisoners in Correctional Facilities and in Community Hospitals: A Cross-Sectional Study. Palliat Med. 2018;32(1):17-22.
  24. Kanzaria HK, Niedzwiecki MJ, Montoy JC, Raven MC, Hsia RY. Persistent Frequent Emergency Department Use: Core Group Exhibits Extreme Levels of Use for More Than a Decade. Health Aff (Millwood). 2017;36(10):1720-1728.
  25. Hsia RY, Niedzwiecki M. Avoidable Emergency Department Visits: A Starting Point. Int J Qual Health Care. 2017;29(5):642-645.
  26. Hsia RY, Sarkar N, Shen YC. Impact of Ambulance Diversion: Black Patients With Acute Myocardial Infarction Had Higher Mortality Than Whites. Health Aff (Millwood). 2017;36(6):1070-1077. 
  27. Shen YC, Chen G, Hsia RY. Community and Hospital Factors Associated with Stroke Center Certification in the United States, 2009-2017. JAMA Netw Open. 2019;2(7):e197855. doi:10.1001/jamanetworkopen.2019.7855.
  28. Hsuan C, Hsia RY, Horwitz J, Ponce NA, Rice T, Needleman J. Ambulance Diversions Following Public Hospital Emergency Department Closures. Health Serv Res. 2019; 00:1-10. doi.org/10.1111/1475-6773.13147.
  29. Castillo EM, Brennan JJ, Howard J, Hsia RY, Chalmers C, Chan TC, Ko KJ. Factors Associated with Geriatric Frequent Users of Emergency Departments. Ann Emerg Med. 2019; pii: S0196-0644(18)31577-4. doi: 10.1016/j.annemergmed.2018.12.013. 
  30. Nath JB, Costigan S, Lin F, Vittinghoff E, Hsia RY. Access to Federally Qualified Health Centers and Emergency Department Use Among Uninsured and Medicaid-insured Adults: California, 2005 to 2013. Acad Emerg Med. 2019; doi: 10.1111/acem.13494.
  31. Niedzwiecki MJ, Kanzaria HK, Montoy JC, Hsia RY, Raven MC. Past Frequent Emergency Department Use Predicts Mortality. Health Aff (Millwood). 2019;38(1):155-158.
  32. Supat B, Brennan JJ, Vilke GM, Ishimine P, Hsia RY, Castillo EM. Characterizing Pediatric High Frequency Users of California Emergency Departments. Am J Emerg Med. 2018;pii: S0735-6757(18)30977-X. doi: 10.1016/j.ajem.2018.12.015. 
  33. Hsia RY, Huang D, Mann NC, Colwell C, Mercer MP, Dai M, Niedzwiecki MJ. A US National Study of the Association Between Income and Ambulance Response Time in Cardiac Arrest. JAMA Netw Open. 2018;1(7):e185202.
  34. Mooney AC, McConville S, Rappaport AJ, Hsia RY. Association of Legal Intervention Injuries with Race and Ethnicity Among Patients Treated in Emergency Departments in California. JAMA Network Open. 2018;1(5):e182150.
  35. Wei R, Mann NC, Dai M, Hsia RY. Injury-Based Geographic Access to Trauma Centers. Acad Emerg Med. 2019;26(2):192-204.
  36. McConville S, Mooney AC, Williams BA, Hsia RY. How Do ED Patients with Criminal Justice Contact Compare to Other ED Users? A Retrospective Analysis of ED Visits in California. BMJ Open. 2018;8:e020897.
  37. Niedzwiecki MJ, Hsia RY, Shen YC. Not All Insurance Is Equal: Differential Treatment and Health Outcomes by Insurance Coverage Among Nonelderly Adult Patients With Heart Attack. J Am Heart Assoc. 2018;7(11):e008152.
  38. McConville S, Raven MC, Sabbagh SH, Hsia RY. Frequent Emergency Department Users: A Statewide Comparison Before and After Affordable Care Act Implementation. Health Aff (Millwood). 2018;37(6):881-889.
  39. Hsia RY, Sarkar N, Shen YC. Impact of Ambulance Diversion: Black Patients with Acute Myocardial Infarction Had Higher Mortality than Whites. Health Affairs. 2017;36(6):1070-1077. 
  40. Shen YC, Hsia RY. Association Between Emergency Department Closure and Treatment, Access, and Health Outcomes Among Patients with Acute Myocardial Infarction. Circulation. 2016;134(20):1597-1599.
  41. Zhu JM, Singhal A, Hsia RY. Emergency Department Length-Of-Stay For Psychiatric Visits Was Significantly Longer Than For Nonpsychiatric Visits, 2002-11. Health Aff (Millwood). 2016; 35(9):1698-1706.
  42. Singhal A, Tien Y, Hsia RY. Racial-Ethnic Disparities in Opioid Prescriptions at Emergency Department Visits for Conditions Commonly Associated with Prescription Drug Abuse. PLOS ONE. 2016; 11(8):e0159224.
  43. Shen YC, Hsia RY. Do Patients Hospitalised in High-Minority Hospitals Experience More Diversion and Poorer Outcomes? A Retrospective Multivariate Analysis of Medicare Patients in California. BMJ Open. 2016; 6(3):e010263.
  44. Wang T, Srebotnjak T, Brownell J, Hsia RY. Emergency department charges for asthma-related outpatient visits by insurance status. J Health Care Poor Underserved. 2014; 25(1):396-405.
  45. Raven MC, Lowe RA, Maselli J, Hsia RY. Comparison of Presenting Complaint vs Discharge Diagnosis for Identifying Nonemergency Emergency Department Visits. JAMA. 2013; 309(11):1145-1153.
  46. Hsia RY, Asch SM, Weiss RE, et al. California Hospitals Serving Large Minority Populations Were More Likely Than Others to Employ Ambulance Diversion. Health Aff (Millwood). 2012; 31(8):1767-1776.
  47. Hsia RY, Srebotnjak T, Kanzaria HK, McCulloch C, Auerbach AD. System-level health disparities in California emergency departments: minorities and Medicaid patients are at higher risk of losing their emergency departments. Ann Emerg Med. 2012; 59:358-365.
  48. Hsia RY, Kellermann A, Shen YC. Factors Associated With Closure of Emergency Departments in the United States. JAMA. 2011; 305(19):1978-1985. 
  49. Hsia RY, Shen YC.  Rising Closures of Trauma Centers Disproportionately Burdens Vulnerable Populations. Health Aff (Millwood). 2011; 30(10):1912-1920. 
  50. Hsia RY, Asch SM, Weiss RE, et al. Hospital Determinants of Emergency Department Left Without Being Seen Rates. Ann Emerg Med. 2011; 58(1):24-32.
  51. Hsia RY, Wang NE, Saynina O, Wise P, Perez-Stable E, Auerbach A. Factors associated with Trauma Center Utilization for Elderly Patients with Trauma: A Statewide Analysis, 1999-2008. Arch Surg. 2011; 146(5):585-592. 
  52. Hsia RY, Shen YC. Possible Geographical Barriers to Trauma Center Access for Underserved Patients in the United States? Arch Surg. 2011; 146(1):1-7. 
  53. Hsia RY, Wang NE, Torres H, Saynina O, Wise P. Disparities in trauma center access despite increasing utilization: Data from California, 1999-2006. J Trauma. 2010; 68(1):217-224.
  54. Shen YC, Hsia, RY. Changes in Emergency Department Access Between 2001 and 2005: Are Vulnerable Populations More at Risk for Declines in Access? Am J Public Health. 2010; 100(8):1462-1469.
  55. Ravikumar D, Hsia RY. Do California counties with lower socioeconomic levels have less access to emergency department care? Acad Emerg Med 2010; 17(5):508-513. 
Emergency Cardiac Care

These studies examine disparities in emergency cardiac care, including ST-elevation myocardial infarction and cardiac arrest, focusing on access, treatment, and outcomes, while exploring the impact of facility availability, socioeconomic and racial inequities, and healthcare system changes on patients.

  1. Shen Y, Feldmeier M, Hsia RY. Non–ST‐Segment–Elevation Myocardial Infarction and ST‐Segment–Elevation Myocardial Infarction Outcomes After a Percutaneous Coronary Intervention–Capable Facility Opening by Patient Race and Community Segregation. Journal of the American Heart Association. 2024;13(22):e035853.
  2. Hsia RY, Shen YC. Structural Inequities In The Adoption Of Percutaneous Coronary Intervention Services By US Hospitals, 2000–20. Health Aff (Millwood). 2024;43(7):1011-1020.
  3. Hsia RY, Redberg RF, Shen YC. Is more better? A multilevel analysis of percutaneous coronary intervention hospital openings and closures on patient volumes. Academic Emergency Medicine. Published online May 16, 2024.
  4. Shen Y, Sarkar N, Hsia RY. Differential Treatment and Outcomes for Patients With Heart Attacks in Advantaged and Disadvantaged Communities. Journal of the American Heart Association. 2023;12(17):e030506.
  5. Ward, MJ., Nikpay, S, Shermeyer, A, Nallamothu, BK, Rokos, I, Self, WH, & Hsia, RY. Interfacility Transfer of Uninsured vs Insured Patients With ST-Segment Elevation Myocardial Infarction in California. JAMA Netw Open. 2023;6(6):e2317831. 
  6. Shen YC, Krumholz HM, Hsia RY. Do PCI Facility Openings and Closures Affect AMI Outcomes Differently in High- vs Average-Capacity Markets? JACC Cardiovasc Interv. 2023;16(10):1129-1140. 
  7. Wang C, Lindquist K, Krumholz H, Hsia RY. Trends in the likelihood of receiving percutaneous coronary intervention in a low-volume hospital and disparities by sociodemographic communities. PLoS One. 2023;18(1):e0279905. eCollection 2023.
  8. Montoy JCC, Shen YC, Hsia RY. Trends in inequities in the treatment of and outcomes for women and minorities with myocardial infarction. Annals of Emergency Medicine. 2022 Aug;80(2):108-117. Epub 2022 Jun 21.
  9. Valdovinos EM, Niedzwiecki MJ, Guo, J, Hsia RY. The association of Medicaid expansion and racial/ethnic inequities in access, treatment, and outcomes for patients with acute myocardial infarction. PLoS ONE. 2020;15(11):e0241785. 
  10. Valdovinos EM, Niedzwiecki MJ, Guo J, Hsia RY. Effects of Medicaid Expansion on Access, Treatment and Outcomes for Patients With Acute Myocardial Infarction. PLoS ONE. 2020;15(4):e0232097.
  11. Hsia RY, Shen YC. Emergency Department Closures And Openings: Spillover Effects On Patient Outcomes In Bystander Hospitals. Health Affairs. 2019; 38(9): 1496-1504.
  12. Hsia RY, Huang D, Mann NC, Colwell C, Mercer MP, Dai M, Niedzwiecki MJ. A US National Study of the Association Between Income and Ambulance Response Time in Cardiac Arrest. JAMA Netw Open. 2018;1(7):e185202.
  13. Hsia RY, Sarkar N, Shen YC. Is Inpatient Volume or Emergency Department Crowding a Greater Driver of Ambulance Diversion? Health Aff (Millwood). 2018; 37(7):1115-1122.
  14. Hsia RY, Huang D, Mann NC, Colwell C, Mercer MP, Dai M, Niedzwiecki MJ. A US National Study of the Association Between Income and Ambulance Response Time in Cardiac Arrest. JAMA Netw Open. 2018;1(7):e185202.
  15. Niedzwiecki MJ, Hsia RY, Shen YC. Not All Insurance Is Equal: Differential Treatment and Health Outcomes by Insurance Coverage Among Nonelderly Adult Patients With Heart Attack. J Am Heart Assoc. 2018;7(11):e008152.
  16. Hsia RY, Sarkar N, Shen YC. Impact of Ambulance Diversion: Black Patients with Acute Myocardial Infarction Had Higher Mortality than Whites. Health Affairs. 2017;36(6):1070-1077. 
  17. Shen YC, Hsia RY. Association Between Emergency Department Closure and Treatment, Access, and Health Outcomes Among Patients with Acute Myocardial Infarction. Circulation. 2016;134(20):1597-1599.
  18. Hsia RY, Shen YC. Percutaneous Coronary Intervention in the United States: Risk Factors for Untimely Access. Health Services Research. 2016; 51(2):592-609.
  19. Shen YC, Hsia RY. Ambulance Diversion Associated With Reduced Access To Cardiac Technology And Increased One-Year Mortality. Health Aff. 2015; 34(8):1273-1280. 
  20. Shen YC, Hsia RY. Does Decreased Access to Emergency Departments Affect Patient Outcomes? Analysis of AMI Population 1996-2005. Health Serv Res. 2012; 47(1):188-210.
  21. Shen YC, Hsia RY.  Association Between Ambulance Diversion and Survival Among Patients With Acute Myocardial Infarction. JAMA. 2011; 305(23):2440-2447.
Emergency Department Crowding and Ambulance Diversions

Emergency department operations—like crowding, ambulance diversion, and length of stay— can affect patient outcomes, healthcare access, and disparities. These projects study contributing factors to crowding as well as the impacts of crowding on patient outcomes as well as ramifications on the larger healthcare system.

  1. Shteyeler VM, Feldmeier M, Bagay RJG, Ballard D, Colwell C, Hsia RY. Racial and Socioeconomic Disparities in California Ambulance Patient Offload Times. JAMA Netw Open. 2025;8(5):e2510325. 
  2. Feldmeier M, Reyes KP, Chen C, Sporer KA, Konik Z, Garzón H, Hsia RY. Patterns in California Ambulance Patient Offload Times by Local Emergency Medical Services Agency. JAMA Netw Open. 2024;7(12):e2451022.
  3. Hsuan C, Segel JE, Hsia RY, Wang Y, Rogowski J. Association of emergency department crowding with inpatient outcomes. Health Serv Res. 2022; 58(4): 828-843. doi: 10.1111/1475-6773.14076.
  4. Hsia RY, Shen YC. Emergency Department Closures And Openings: Spillover Effects On Patient Outcomes In Bystander Hospitals. Health Affairs. 2019; 38(9): 1496-1504.
  5. Hsuan C, Hsia RY, Horwitz J, Ponce NA, Rice T, Needleman J. Ambulance Diversions Following Public Hospital Emergency Department Closures. Health Serv Res. 2019; 00:1-10. doi.org/10.1111/1475-6773.13147.
  6. Hsia RY, Sarkar N, Shen YC. Is Inpatient Volume or Emergency Department Crowding a Greater Driver of Ambulance Diversion? Health Aff (Millwood). 2018; 37(7):1115-1122.
  7. Hsia RY, Sarkar N, Shen YC. Impact of Ambulance Diversion: Black Patients with Acute Myocardial Infarction Had Higher Mortality than Whites. Health Affairs. 2017;36(6):1070-1077. 
  8. Shen YC, Hsia RY. Do Patients Hospitalised in High-Minority Hospitals Experience More Diversion and Poorer Outcomes? A Retrospective Multivariate Analysis of Medicare Patients in California. BMJ Open. 2016; 6(3):e010263.
  9. Sabbatini AK, Kocher KE, Basu A, Hsia RY. In-Hospital Outcomes and Costs Among Patients Hospitalized During a Return Visit to the Emergency Department. JAMA. 2016; 315(7):663-671.
  10. Shen YC, Hsia RY. Ambulance Diversion Associated With Reduced Access To Cardiac Technology And Increased One-Year Mortality. Health Aff. 2015; 34(8):1273-1280. 
  11. Kanzaria HK, Probst MA, Ponce NA, Hsia RY. The association between advanced diagnostic imaging and ED length of stay. American Journal of Emergency Medicine. 2014; 32(10):1253–1258.
  12. Carrier E, Khaldun J, Hsia RY. Association Between Emergency Department Length of Stay and Rates of Admission to Inpatient and Observation Services. JAMA Intern Med. 2014; 174(11):1843-1846.
  13. Le S, Hsia RY. Timeliness of Care in U.S. Emergency Departments: An Analysis of Newly Released Metrics From the Centers for Medicare & Medicaid Services. JAMA Intern Med. 2014; 174(11):1847-1849.
  14. Handel DA, Fu R, Vu E, Augustine JJ, Hsia RY, Shufflebarger CM, Sun B. Association of Emergency Department and Hospital Characteristics with Elopements and Length of Stay. J Emerg Med. 2014; 46(6):839-846.
  15. Hsia RY, Asch SM, Weiss RE, et al. Is Emergency Department Crowding Associated With Increased "Bounce-back" Admissions? Med Care. 2013; 51(11):1008-1014.
  16. Xu M, Wong TC, Wong SY, Chin KS, Tsui KL, Hsia RY. Delays in Service for Non-Emergent Patients Due to Arrival of Emergent Patients in the Emergency Department: A Case Study in Hong Kong. J Emerg Med. 2013; 45(2):271-280.
  17. Sun BC, Hsia RY, Weiss RE, et al. Effect of Emergency Department Crowding on Outcomes of Admitted Patients. Ann Emerg Med. 2013; 61(6):605-611.e6.
  18. Gabayan GZ, Asch SM, Hsia RY, et al. Factors associated with short-term bounce-back admissions after emergency department discharge. Ann Emerg Med. 2013; 62(2):136-144.e1.
  19. Fee C, Burstin H, Maselli JH, Hsia RY. Association of emergency department length of stay with safety net status. JAMA 2012; 307(5):476-482.
  20. Hsia RY, Asch SM, Weiss RE, et al. Hospital Determinants of Emergency Department Left Without Being Seen Rates. Ann Emerg Med. 2011; 58(1):24-32.
  21. Shen YC, Hsia RY. Association Between Ambulance Diversion and Survival Among Patients With Acute Myocardial Infarction. JAMA. 2011; 305(23):2440-2447.
Geospatial Analysis of Healthcare Services

These studies use geospatial analysis (e.g., the process of converting addresses into geographic coordinates) to understand geographical trends and patterns in emergency service access. We also examine how regionalization impacts patient outcomes and highlight inequities to inform policy solutions.

  1. Hsia RY, Sarkar N, Shen YC. Provision of Stroke Care Services by Community Disadvantage Status in the US, 2009-2022. JAMA Netw Open. 2024;7(7):e2421010.
  2. Hsia RY, Shen YC. Structural Inequities In The Adoption Of Percutaneous Coronary Intervention Services By US Hospitals, 2000-20. Health Affairs. 2024;43(7):1011-1020.
  3. Shen Y, Sarkar N, Hsia RY. Differential Treatment and Outcomes for Patients With Heart Attacks in Advantaged and Disadvantaged Communities. Journal of the American Heart Association. 2023;12(17):e030506.
  4. Shen YC, Krumholz HM, Hsia RY. Do PCI Facility Openings and Closures Affect AMI Outcomes Differently in High- vs Average-Capacity Markets? JACC Cardiovasc Interv. 2023;16(10):1129-1140. 
  5. Furmanchuk A, James Rydland K, Hsia RY, et al. Geographic Disparities in Re-triage Destinations Among Seriously Injured Californians. Ann Surg Open. 2023;4(1):e270. 
  6. Wang C, Lindquist K, Krumholz H, Hsia RY. Trends in the likelihood of receiving percutaneous coronary intervention in a low-volume hospital and disparities by sociodemographic communities. PLoS One. 2023;18(1):e0279905. eCollection 2023.
  7. Shen YC, Sarkar N, Hsia RY. Structural inequities for historically underserved communities in the adoption of stroke certification in the United States. JAMA Neurology. 2022;79(8):777-786. Online ahead of print.
  8. Ormseth CH, Mooney AC, Mitchell O, Hsia RY. Association of residential racial and ethnic segregation with legal intervention injuries in California. JAMA Netw Open. 2022;5(6):e2219217. 
  9. Hsia RY, Shen YC, Krumholz H. Association of cardiac care regionalization with access, treatment, and mortality among patients with ST-elevation myocardial infarction. Circ Cardiovasc Qual Outcomes. 2021;14(3):e007195. 
  10. Shen YC, Hsia RY. Differential benefits of cardiac care regionalization based on driving time to percutaneous coronary intervention. Acad Emerg Med. 2020;28(5):519-529.
  11. Hsia RY, Krumholz HM, Shen YC. Evaluation of STEMI regionalization on access, treatment, and outcomes among adults living in nonminority and minority communities. JAMA Netw Open. 2020;3(11):e2025874.
  12. Hsia RY, Shen YC. Emergency Department Closures And Openings: Spillover Effects On Patient Outcomes In Bystander Hospitals. Health Affairs. 2019;38(9):1496-1504.
  13. Hsuan C, Hsia RY, Horwitz J, Ponce NA, Rice T, Needleman J. Ambulance Diversions Following Public Hospital Emergency Department Closures. Health Serv Res. 2019;54(4):870-879.
  14. Wei R, Mann NC, Dai M, Hsia RY. Injury-Based Geographic Access to Trauma Centers. Acad Emerg Med. 2019;26(2):192-204.
  15. Hsia RY, Dai M, Wei R, Sabbagh S, Mann NC. Geographic Discordance Between Patient Residence and Incident Location in Emergency Medical Services Responses. Ann Emerg Med. 2017;69(1):44-51.e3.
  16. Wandling M, Behrens J, Hsia RY, Crandall M. Geographic Disparities in Access to Urban Trauma Care: Defining the Problem and Identifying a Solution for Gunshot Wound Victims in Chicago. Am J Surg. 2016;212(4):587-591.
  17. Shen YC, Hsia RY. Association Between Emergency Department Closure and Treatment, Access, and Health Outcomes Among Patients with Acute Myocardial Infarction. Circulation. 2016;134(20):1597-1599.
  18. Hsia RY, Shen YC. Percutaneous Coronary Intervention in the United States: Risk Factors for Untimely Access. Health Services Research. 2016; 51(2):592-609.
  19. Crandall M, Sharp D, Wei X, Nathens A, Hsia RY. Effects of Closure of an Urban Level 1 Trauma Centre on Adjacent Hospitals and Local Injury Mortality: A Retrospective, Observational Study. BMJ Open. 2016; 6(5):e011700.
  20. Shen YC, Hsia RY. Do Patients Hospitalised in High-Minority Hospitals Experience More Diversion and Poorer Outcomes? A Retrospective Multivariate Analysis of Medicare Patients in California. BMJ Open. 2016; 6(3):e010263.
  21. Choi JC, Hsia RY, Kim AS. Regional availability of mechanical embolectomy for acute ischemic stroke in California, 2009 to 2010. Stroke. 2015;46(3):762-768.
  22. Shen YC, Hsia RY. Ambulance Diversion Associated With Reduced Access To Cardiac Technology And Increased One-Year Mortality. Health Aff. 2015; 34(8):1273-1280. 
  23. Liu C, Srebotnjak T, Hsia RY. California emergency department closures are associated with increased inpatient mortality at nearby hospitals. Health Aff (Millwood). 2014;33(8):1323-1329.
  24. Hsia RY, Srebotnjak T, Maselli J, Crandall M, McCulloch C, Kellermann AL. The Association of Trauma Center Closures with Increased Inpatient Mortality for Injured Patients. J Trauma Acute Care Surg. 2014; 76(4):1048-1054.
  25. Crandall M, Sharp D, Unger E, Straus D, Brasel K, Hsia R, Esposito T. Trauma Deserts: Distance from a Trauma Center, Transport Times, and Mortality from Gunshot Wounds in Chicago. Am J Public Health. 2013; 103(6):1103-1109.
  26. Hsia RY, Kanzaria HK, Srebotnjak T, Maselli J, McCulloch C, Auerbach AD. Is emergency department closure resulting in increased distance to the nearest emergency department associated with increased inpatient mortality? Ann Emerg Med. 2012;60(6):707-715.e4.
  27. Shen YC, Hsia RY. Does Decreased Access to Emergency Departments Affect Patient Outcomes? Analysis of AMI Population 1996-2005. Health Serv Res. 2012; 47(1):188-210.
  28. Hsia RY, Kellermann A, Shen YC. Factors Associated With Closure of Emergency Departments in the United States. JAMA. 2011; 305(19):1978-1985. 
  29. Hsia RY, Shen YC. Rising Closures of Trauma Centers Disproportionately Burdens Vulnerable Populations. Health Aff (Millwood). 2011; 30(10):1912-1920. 
  30. Hsia RY, Shen YC. Possible Geographical Barriers to Trauma Center Access for Underserved Patients in the United States? Arch Surg. 2011; 146(1):1-7. 
  31. Shen YC, Hsia RY. Association Between Ambulance Diversion and Survival Among Patients With Acute Myocardial Infarction. JAMA. 2011; 305(23):2440-2447.
  32. Shen YC, Hsia, RY. Changes in Emergency Department Access Between 2001 and 2005: Are Vulnerable Populations More at Risk for Declines in Access? Am J Public Health. 2010; 100(8):1462-1469.
  33. Ravikumar D, Hsia RY. Do California counties with lower socioeconomic levels have less access to emergency department care? Acad Emerg Med 2010; 17(5):508-513.
Geriatric

This category examines trauma and emergency care for elderly patients, highlighting injuries, reduced access to trauma centers, and frequent emergency department visits. 

  1. Castillo EM, Brennan JJ, Howard J, Hsia RY, Chalmers C, Chan TC, Ko KJ. Factors Associated with Geriatric Frequent Users of Emergency Departments. Ann Emerg Med. 2019; 74(2): 270-275.
  2. Newgard CD, Holmes JF, Haukoos JS, Bulger EM, Staudenmayer K, Wittwer L, Stecker E, Dai M, Hsia RY. Improving Early Identification of the High-Risk Elderly Trauma Patient By Emergency Medical Services. Injury. 2016; 47(1):19-25.
  3. Brownell J, Wang J, Smith A, Stephens C, Hsia RY. Trends in Emergency Department Visits for Ambulatory Care Sensitive Conditions by Elderly Nursing Home Residents, 2001-2009. JAMA Intern Med. 2014; 174(1):156-158.
  4. Hsia RY, Wang NE, Saynina O, Wise P, Perez-Stable E, Auerbach A. Factors associated with Trauma Center Utilization for Elderly Patients with Trauma: A Statewide Analysis, 1999-2008. Arch Surg. 2011; 146(5):585-592.
Global

This research focuses on improving access to emergency care and health services on a global scale, examining infrastructure gaps and policy strategies to address health disparities and strengthen systems. 

  1. Duffy J, Jones P, McNaughton CD, Ling V, Matelski J, Hsia RY, et al. Emergency department utilization, admissions, and revisits in the United States (New York), Canada (Ontario), and New Zealand: A retrospective cross-sectional analysis. Acad Emerg Med. 2023;30(0):946-954. 
  2. Mock CN, Donkor P, Gawande A, Jamison DT, Kruk ME, Debas HT, and the DCP3 Essential Surgery Author Group. Essential surgery: key messages from Disease Control Priorities, 3rd edition. Lancet. 2015; 385(9983):2209-2219. 
  3. Hsia RY, Thind A, Zakariah A, Hicks E, Mock C. Prehospital and emergency care: Updates from the Disease Control Priorities, Version 3. World Journal of Surgery. 2015; 39(9):2161-2167.
  4. Xu M, Wong TC, Wong SY, Chin KS, Tsui KL, Hsia RY. Delays in Service for Non-Emergent Patients Due to Arrival of Emergent Patients in the Emergency Department: A Case Study in Hong Kong. J Emerg Med. 2013; 45(2):271-280.
  5. Sani R, Nameoua B, Yahaya A, Hassane I, Adamou R, Hsia RY, Joekman P, Sako A, Habibou A. Provisional surgical training programs for increasing surgical capacity in rural areas in Niger: reply to letter. World J Surg. 2011; 35(3):693. 
  6. Hsia RY, Mbembati NA, Macfarlane S, Kruk ME. Access to Emergency and Surgical Care in sub-Saharan Africa: The Infrastructure Gap. Health Policy Plan. 2011; 27(3):234-244.
  7. Hsia RY, Ozgediz D, Jayaraman S, Mutto M, Jayaraman S, Kyamanywa P, Kobusingye O. Epidemiology of Child injuries in Uganda: Challenges for health policy. J Public Health Africa. 2011; 2(1):e15.
  8. Jayaraman S, Ozgediz D, Miyamoto J, Caldwell N, Lipnick M, Mijumbi C, Mabweijano JR, Hsia RY, Dicker R. Disparities in Injury Mortality between Uganda and the United States: Comparative Analysis of a Neglected Disease. World J Surg. 2011; 35:505–511.
  9. McQueen K, Ozgediz D, Riviello R, Hsia RY, Jayaraman S, Sullivan S, Meara J. Essential surgery: Integral to the right to health. Health Hum Rights. 2010; 12(1):137-152. 
  10. Hsia RY, Ozgediz D, Mutto M, Jayaraman S, Kyamanywa P, Kobusingye O. Epidemiology of Injuries Presenting to the National Hospital in Kampala, Uganda: Implications for Research and Policy. Int J Emerg Med. 2010; 3:165-172.
  11. Bickler S, Ozgediz D, Gosselin R, Weiser T, Spiegel D, Hsia RY, Dunbar P, McQueen K, Jamison D. Key concepts for estimating the burden of surgical conditions and the unmet need for surgical care. World J Surg. 2010; 34(3):374-380.
  12. Kruk ME, Wladis A, Mbembati N, Ndao-Brumblay SK, Hsia RY, et al. Human resource and funding constraints for essential surgery in district hospitals in Africa. PLoS Med. 2010; 7(3):e1000242.
  13. Hsia RY, Razzak J, Tsai AC, Hirshon JM. Placing Emergency Care on the Global Health Research Agenda. Ann Emerg Med. 2010; 56(2):142-149. 
  14. Riviello R, Ozgediz D, Hsia RY, Azzie G, Newton M, Tarpley J. The Role of Collaborative Academic Partnerships in Surgical Training, Education and Provision. World J Surg. 2010; 34(3):459-465.
  15. Luboga S, Macfarlane SB, von Schreeb J, Kruk ME, Cherian MN, Bergström S, Bossyns P, Denerville E, Dovlo D, Galukande M, Hsia RY, et al. Increasing Access to Surgical Services in Sub-Saharan Africa: Priorities for National and International Agencies Recommended by the Bellagio Essential Surgery Group. PLoS Medicine. 2009; 6(12):e1000200, 1-5. 
  16. Jayaraman S, Mabweijano JR, Lipnick M, Caldwell N, Miyamoto J, Wangoda R, Mijumbi C, Hsia RY, Dicker R, Ozgediz D. First things first: effectiveness and scalability of a basic prehospital trauma care program for lay first-responders in Kampala, Uganda. PLoS One. 2009; 4(9):e6955, 1-7. 
  17. Jayaraman S, Mabweijano JR, Lipnick M, Caldwell N, Miyamoto J, Wangoda R, Mijumbi C, Hsia RY, Dicker R, Ozgediz D. Current Patterns of Prehospital Trauma Care in Kampala, Uganda and the Feasibility of a Lay-First-Responder Training Program. World J Surg. 2009; 33:2512–2521.
  18. Sani R, Nameoua B, Yahaya A, Hassane I, Adamou R, Hsia RY, Hoekman P, Sako A, Habibou A. The impact of launching of surgery at the district level in Niger. World J Surg. 2009; 33:2063–2068. 
  19. Ozgediz D, Hsia RY, Weiser T, et al. Population Health Metrics for Surgery: Effective Coverage of Surgical Services in Low-Income and Middle-Income Countries. World J Surg. 2009; 33(1):1-5. 
Pediatrics

This research focuses on pediatric emergency care, examining trends in access, utilization, outcomes, and disparities, with particular attention to key factors that influence frequent emergency department use and hospital readmissions for pediatric emergency care. 

  1. Hsia RY, Mannix RC, Guo J, Kornblith AE, Lin F, Sokolove P, Manley GT. Revisits, Readmissions, and Outcomes for Pediatric Traumatic Brain Injury in California, 2005-2014. PLoS One. 2020;15(1):e0227981.  
  2. Wei R, Mann NC, Dai M, Hsia RY. Injury-Based Geographic Access to Trauma Centers. Acad Emerg Med. 2019;26(2):192-204.
  3. Supat B, Brennan JJ, Vilke GM, Ishimine P, Hsia RY, Castillo EM. Characterizing Pediatric High Frequency Users of California Emergency Departments. Am J Emerg Med. 2019;37(9),1699-1704. 
  4. Samuels-Kalow ME, Niedzwiecki M, Friedman AB, Sokolove PE, Hsia RY. Comparing Resource Use Between Paediatric Emergency Department Visits by Triage Level. Emerg Med J. 2018;35(11):681-684.
  5. Kaiser SV, Lam R, Joseph GB, McCulloch C, Hsia RY, Cabana MD, Bardach NS. Limitations of Using Pediatric Respiratory Illness Readmissions to Compare Hospital Performance. J Hosp Med. 2018; doi 10.12788/jhm.2988.
  6. Nath JB, Costigan S, Lin F, Vittinghoff E, Hsia RY. Federally Qualified Health Center Access and Emergency Department Use Among Children. Pediatrics. 2016; 138(4):e20160479.
  7. Nath JB, Hsia RY. Children’s Emergency Department Use for Asthma, 2001-2010. Academic Pediatrics. 2015; 15(2):225-230.
  8. Newgard C, Kuppermann N, Holmes JF, Haukoos J, Wetzel B, Hsia RY, Wang NE, Bulger EM, Staudenmeyer K, Mann NC, Barton E, Wintemute GJ. Gunshot Injuries in Children Served by Emergency Services. Pediatrics. 2013; 132(5):862-870. 
  9. Hsia RY, MacIsaac D, Palm E, Baker LC. Trends in charges and payments for non-hospitalized emergency department pediatric visits, 1996-2003. Acad Emerg Med. 2008; 15(4):347-354.
Quality Measurement

This research focuses on quality measurement in emergency care, examining trends, disparities, and outcomes in emergency department utilization.  

  1. Duffy J, Jones P, McNaughton CD, Ling V, Matelski J, Hsia RY, et al. Emergency department utilization, admissions, and revisits in the United States (New York), Canada (Ontario), and New Zealand: A retrospective cross-sectional analysis. Acad Emerg Med. 2023;30(9):946-954. 
  2. Cox DD, Subramony R, Supat B, Brennan JJ, Hsia RY, Castillo EM. Geriatric falls: patient characteristics associated with emergency department revisits. WestJEM. 2022;23(5):734-738.
  3. Baehr A, Fought AJ, Hsia RY, Wiler JL, Ginde AA. The association between area deprivation index and emergency department discharge rates and revisits. Academic Emergency Medicine. 2022;29(7):902-904.
  4. Hsuan C, Carr BG, Hsia RY, Hoffman GJ. Assessment of Hospital Readmissions From the Emergency Department After Implementation of Medicare’s Hospital Readmissions Reduction Program. JAMA Netw Open. 2020;3(5):e203857.
  5. Hsia RY, Mannix RC, Guo J, et al. Revisits, readmissions, and outcomes for pediatric traumatic brain injury in California, 2005-2014. PLoS One. 2020;15(1):e0227981.
  6. McConville S, Raven MC, Sabbagh SH, Hsia RY. Frequent emergency department users: a statewide comparison before and after affordable care act implementation. Health Aff (Millwood). 2018;37(6):881-889.
  7. Kaiser SV, Lam R, Joseph GB, McCulloch C, Hsia RY, Cabana MD, Bardach NS. Limitations of Using Pediatric Respiratory Illness Readmissions to Compare Hospital Performance. J Hosp Med. 2018;13(11):737-742.
  8. Hsia RY, Markowitz AJ, Lin F, Guo J, Madhok DY, Manley GT. Ten-year trends in traumatic brain injury: a retrospective cohort study of California emergency department and hospital revisits and readmissions. BMJ Open. 2018;8(12):e022297.
  9. Sabbatini AK, Kocher KE, Basu A, Hsia RY. In-Hospital Outcomes and Costs Among Patients Hospitalized During a Return Visit to the Emergency Department. JAMA. 2016;315(7):663-671.
  10. Schuur JD, Hsia RY, Burstin H, Schull MJ, Pines JM. Quality Measurement In The Emergency Department: Past And Future. Health Aff (Millwood). 2013;32(12):2129-2138.
  11. Jayaraman S, Ozgediz D, Miyamoto J, Caldwell N, Lipnick M, Mijumbi C, Mabweijano JR, Hsia RY, Dicker R. Disparities in injury mortality between Uganda and the United States: comparative analysis of a neglected disease. World J Surg. 2011;35(3):505–511.
Regionalized Systems of Care

Regionalization of healthcare services is the deliberate organization and coordination of healthcare resources to ensure patients receive the right care at the right place at the right time. As emergency care is highly dependent on geographical location and proximity to hospital systems, this research focuses on regionalized care systems for time-sensitive conditions such as trauma, ST-elevation myocardial infarction, and stroke, exploring geographic disparities, certification processes, and factors influencing emergency care utilization.

  1. Feldmeier M, Kim AS, Zachrison KS, Alberts MJ, Shen YC, Hsia RY. Heterogeneity of State Stroke Center Certification and Designation Processes. Stroke. 2024;55(4):1051-1058.
  2. Hsia RY, Krumholz H, Shen Y-C. Evaluation of STEMI Regionalization on Access, Treatment, and Outcomes Among Adults Living in Nonminority and Minority Communities. JAMA Netw Open. 2020;3(11):e2025874. 
  3. Vashi A, Carr BC, Urech, Greene, Warsavage T, Hsia RY, Asch S. Identification of Emergency Care Sensitive Conditions and Factors Associated with Emergency Department Utilization. JAMA Netw Open. 2019 Aug 2;2(8):e198642. 
  4. Shen YC, Chen G, Hsia RY. Community and Hospital Factors Associated with Stroke Center Certification in the United States, 2009-2017. JAMA Netw Open. 2019;2(7):e197855. 
  5. Hsia RY, Sabbagh S, Sarkar N, Sporer K, Rokos IC, Brown JF, Brindis RG, Guo J, Shen YC. Trends in Regionalization of Care for ST-Segment Elevation Myocardial Infarction. West J Emerg Med. 2017;18(6):1010-1017.
  6. Hsia RY, Dai M, Wei R, Sabbagh S, Mann NC. Geographic Discordance Between Patient Residence and Incident Location in Emergency Medical Services Responses. Ann Emerg Med. 2017;69(1):44-51.e3.
  7. Rokos IC, Sporer K, Savino PB, Mercer MP, Shontz S, Sabbagh S, Hsia RY. A Novel Tool to Quantify the Degree and Duration of STEMI Regionalization across California. Crit Pathw Cardiol. 2016; 15(3):103-105.
  8. Pilgrim R, Hilton J, Carrier E, Pines JM, Hufstetler G, Thorby S, Milling TJ, Cesta B, Hsia RY. Research Priorities for Administrative Challenges of Integrated Networks of Care. Acad Emerg Med. 2010;17(12):1330-1336.
Stroke and Neurologic Emergencies

This research examines patterns of market-based stroke center certification as well as the impact of these certifications and service provision on patient outcomes, with a focus on addressing structural inequities and improving access for historically underserved communities.

  1. Johnson KL, Wood AJ, Hsia RY, Guterman EL. Characterizing emergency department and inpatient health care utilization after seizure-related hospitalization: A retrospective cohort study. Epilepsia. 2024;65(3):698-708.  
  2. Shen YC, Kim AS, Hsia RY. Treatments and Patient Outcomes Following Stroke Center Expansion. JAMA Network Open. 2024;7(11):e2444683.
  3. Hsia RY, Sarkar N, Shen YC. Provision of Stroke Care Services by Community Disadvantage Status in the US, 2009-2022. JAMA Netw Open. 2024;7(7):e2421010.
  4. Feldmeier M, Kim AS, Zachrison KS, Alberts MJ, Shen YC, Hsia RY. Heterogeneity of State Stroke Center Certification and Designation Processes. Stroke. 2024;55(4):1051-1058.
  5. Shen YC, Sarkar N, Hsia RY. Structural inequities for historically underserved communities in the adoption of stroke certification in the United States. JAMA Neurology. 2022;79(8):777-786. 
  6. Shen YC, Chen G, Hsia RY. Community and Hospital Factors Associated with Stroke Center Certification in the United States, 2009-2017. JAMA Netw Open. 2019;2(7):e197855. 
Trauma

These are studies looking at trauma patients, defined as people who have suffered a physical injury that may be minor, serious, life-threatening, or potentially life-threatening, as well as evaluating trauma care systems. 

  1. Wang Y, Liu V, Wang Y, Bai G, Hsia RY. Emergency Department Trauma Activation Fees by Payer Type. JAMA Surg. 2024;159(6):718-720.
  2. Shi M, Reddy S, Furmanchuk A, Holl JL, Hsia RY, Mackersie RC, Bilimoria KY, Stey AM. Re-triage moderates association between state trauma funding and lower mortality of trauma patients. Injury. 2023;54(9):110859.
  3. Furmanchuk A, James Rydland K, Hsia RY, et al. Geographic Disparities in Re-triage Destinations Among Seriously Injured Californians. Ann Surg Open. 2023;4(1):e270. 
  4. Hsia RY, Markowitz AJ, Lin F, Guo J, Madhok DY, Manley GT. Ten-year Trends in Traumatic Brain Injury: A Retrospective Cohort Study of California Emergency Department and Hospital Revisits and Readmissions. BMJ Open. 2018;8:e022297.
  5. Uribe-Leitz T, Esquivel MM, Knowlton LM, Ciesla D, Lin F, Hsia RY, Spain DA, Winchell RJ, Staudenmayer KL. The American College of Surgeons (ACS) Needs-Based Assessment of Trauma Systems (NBATS): Estimates for the State of California. J Trauma Acute Care Surg. 2017;82(5):861-866.
  6. Fleischman RJ, Mann NC, Dai M, Holmes JF, Wang NE, Haukoos J, Hsia RY, Rea T, Newgard CD. Validating the Use of ICD-9 Code Mapping to Generate Injury Severity Scores. J Trauma Nurs. 2017;24(1):4-14.
  7. Hsia RY, Dai M, Wei R, Sabbagh S, Mann NC. Geographic Discordance Between Patient Residence and Incident Location in Emergency Medical Services Responses. Ann Emerg Med. 2017;69(1):44-51.e3.
  8. Wandling M, Behrens J, Hsia RY, Crandall M. Geographic Disparities in Access to Urban Trauma Care: Defining the Problem and Identifying a Solution for Gunshot Wound Victims in Chicago. Am J Surg. 2016;212(4):587-591.
  9. Crandall M, Sharp D, Wei X, Nathens A, Hsia RY. Effects of Closure of an Urban Level 1 Trauma Centre on Adjacent Hospitals and Local Injury Mortality: A Retrospective, Observational Study. BMJ Open. 2016; 6(5):e011700.
  10. Tong GE, Staudenmayer K Lin F, Hsia RY. Use of Emergency Department Imaging in Patients with Minor Trauma. J Surg Res. 2016; 203(1):238-245.
  11. Newgard CD, Holmes JF, Haukoos JS, Bulger EM, Staudenmayer K, Wittwer L, Stecker E, Dai M, Hsia RY. Improving Early Identification of the High-Risk Elderly Trauma Patient By Emergency Medical Services. Injury. 2016; 47(1):19-25.
  12. Staudenmayer K, Lin F, Weiser T, Maggio P, Mackersie R, Spain D, Hsia RY. The Triage of Injured Patients: Mechanism of Injury, Regardless of Injury Severity, Determines Hospital Destination. Am Surg. 2016; 82(4):356-361. 
  13. Zocchi M, Hsia RY, Carr B, Sarani B, Pines J. Comparison of Mortality and Costs at Trauma and Non-Trauma Centers for Minor and Moderately Severe Injuries in California. Ann Emerg Med. 2016; 67(1):56-67.e5.
  14. Hsia RY, Srebotnjak T, Maselli J, Crandall M, McCulloch C, Kellermann AL. The Association of Trauma Center Closures with Increased Inpatient Mortality for Injured Patients. J Trauma Acute Care Surg. 2014; 76(4):1048-1054.
  15. Staudenmayer K, Lin F, Mackersie R, Spain D, Hsia R. Variability in California Triage from 2005 to 2009: A Population-Based Longitudinal Study of Severely Injured Patients. J Trauma Acute Care Surg. 2014; 76(4):1041-1047.
  16. Newgard CD, Richardson D, Holmes JF, Rea TD, Hsia RY, Mann NC, Staudenmayer K, Barton ED, et al. Physiologic Field Triage Criteria For Identifying Seriously Injured Older Adults. Prehosp Emerg Care. 2014; 18(4):461-470.
  17. Dean D, Wezel B, White N. Kupperman N, Wang NE, Haukoos JS, Hsia RY, Mann NC, Barton ED, Newgard CD. From 9-1-1 call to Death: Evaluating Traumatic Deaths in 7 Regions for Early Recognition of High-Risk Patients. J Trauma Acute Care Surg. 2014; 76(3):846-853.
  18. Newgard C, Staudenmeyer K, Hsia RY, et al. The Cost of Over-triage: More Than One-Third of Low-Risk Injured Patients Were Taken to Major Trauma Centers. Health Aff (Millwood). 2013; 32(9):1591-1599.
  19. Staudenmayer KL, Hsia RY, Mann NC, Spain DA, Newgard CD. Triage of Elderly Trauma Patients:  A Population-Based Perspective. J Am Coll Surg. 2013;217(4):569-576.
  20. Newgard C, Mann NC, Hsia RY, Bulger EM, Ma OJ Staudenmeyer K, Haukoos JS, Sahni R, Kuppermann N. Patient Choice in the Selection of Hospitals by 9-1-1 Emergency Medical Services Providers in Trauma Systems. Acad Emerg Med. 2013;20(9):911-919.
  21. Haukoos J, Wetzel B, Hsia R, Wang NE, Bulger EM, Staudenmeyer K, Mann NC, Barton E, Wintemute GJ. Gunshot Injuries in Children Served by Emergency Services. Pediatrics. 2013;132(5):862-870. 
  22. Barnett AS, Wang NE, Sahni S, Hsia RY, Haukoos JS, Barton ED, Holmes JF, Newgard CD. Variation in Prehospital Use and Uptake of the National Field Triage Decision Scheme. Prehosp Emerg Care. 2013;17(2):135-148.
  23. Newgard C, Hsia RY, Mann NC, Schmidt T, Sahni R, Bulger EM, Wang NE, Holmes JF, Fleischman R, Zive D, Staudenmeyer K, Haukoos JS, Kuppermann N. The trade-offs in field trauma triage: a multiregion assessment of accuracy metrics and volume shifts associated with different triage strategies. J Trauma Acute Care Surg. 2013; 74(5):1298-1306.
  24. Crandall M, Sharp D, Unger E, Straus D, Brasel K, Hsia R, Esposito T. Trauma Deserts: Distance from a Trauma Center, Transport Times, and Mortality from Gunshot Wounds in Chicago. Am J Public Health. 2013; 103(6):1103-1109.
  25. Nishijima DK, Haukoos JS, Newgard CD, Staudenmayer K, White N, Slattery D, Maxim PC, Gee CA, Hsia RY, Melnikow JA, Holmes JF. Variability of ICU use in adult patients with minor traumatic intracranial hemorrhage. Ann Emerg Med. 2013;61(5):509-517.
  26. Nakamura Y, Daya M, Buler E, Schreiber M, Mackersie R, Haukoos J, Barton E, Sturges Z, Hsia RY, Holmes JF, et al. Evaluating Age in the Field Triage of Injured Persons. Ann Emerg Med. 2012;60(3):335-345.
  27. Newgard CD, Kampp M, Nelson M, Holmes JF, Zive D, Rea T, Bulger EM, Liao M, Sherck J, Hsia RY, et al Deciphering the Use and Predictive Value of “EMS Provider Judgment” in Out-of-Hospital Trauma Triage: A Multi-site, Mixed Methods Assessment. J Trauma Acute Care Surg. 2012;72(5):1239-1248.
  28. Newgard C, Malveau S, Staudenmayer K, Wang NE, Hsia RY, Mann NC, et al. Evaluating the use of existing data sources, probabilistic linkage, and multiple imputation to build population-based injury databases across phases of trauma care. Acad Emerg Med. 2012;19(4):469-480.
  29. Staudenmayer K, Hsia R, Wang N, et al. The Forgotten Trauma Patient: Outcomes for Injured Patients Evaluated by Emergency Medical Services but not Transported to the Hospital. J Trauma Acute Care Surg. 2012; 72(3):594-600.
  30. Hsia RY, Shen YC. Possible Geographical Barriers to Trauma Center Access for Underserved Patients in the United States? Arch Surg. 2011;146(1):1-7. 
  31. Newgard CD, Zive D, Holmes JF, Bulger EM, Staudenmayer K, Liao M, Rea T, Hsia RY, Wang NE, Fleischman R, Jui J, Mann NC, Haukoos JS, Sporer KA, Gubler KD, Hedges JR. A multisite assessment of the American college of surgeons committee on trauma field triage decision scheme for identifying seriously injured children and adults. J Am Coll Surg. 2011;213(6):709-721.
  32. Hsia RY, Shen YC. Rising Closures of Trauma Centers Disproportionately Burdens Vulnerable Populations. Health Aff (Millwood). 2011;30(10):1912-1920.
  33. Hsia RY, Wang NE, Saynina O, Wise P, Perez-Stable E, Auerbach A. Factors associated with Trauma Center Utilization for Elderly Patients with Trauma: A Statewide Analysis, 1999-2008. Arch Surg. 2011;146(5):585-592. 
  34. Hsia RY, Wang NE, Torres H, Saynina O, Wise P. Disparities in trauma center access despite increasing utilization: Data from California, 1999-2006. J Trauma. 2010; 68(1):217-224.