Journal of General Internal Medicine

, Volume 28, Issue 3, pp 459–465 | Cite as

Patient Sharing Among Physicians and Costs of Care: A Network Analytic Approach to Care Coordination Using Claims Data

  • Craig Evan Pollack
  • Gary E. Weissman
  • Klaus W. Lemke
  • Peter S. Hussey
  • Jonathan P. Weiner
Original Research



Improving care coordination is a national priority and a key focus of health care reforms. However, its measurement and ultimate achievement is challenging.


To test whether patients whose providers frequently share patients with one another—what we term ‘care density’—tend to have lower costs of care and likelihood of hospitalization.


Cohort study


9,596 patients with congestive heart failure (CHF) and 52,688 with diabetes who received care during 2009. Patients were enrolled in five large, private insurance plans across the US covering employer-sponsored and Medicare Advantage enrollees


Costs of care, rates of hospitalizations


The average total annual health care cost for patients with CHF was $29,456, and $14,921 for those with diabetes. In risk adjusted analyses, patients with the highest tertile of care density, indicating the highest level of overlap among a patient’s providers, had lower total costs compared to patients in the lowest tertile ($3,310 lower for CHF and $1,502 lower for diabetes, p < 0.001). Lower inpatient costs and rates of hospitalization were found for patients with CHF and diabetes with the highest care density. Additionally, lower outpatient costs and higher pharmacy costs were found for patients with diabetes with the highest care density.


Patients treated by sets of physicians who share high numbers of patients tend to have lower costs. Future work is necessary to validate care density as a tool to evaluate care coordination and track the performance of health care systems.


care coordination performance measure provider social networks care density 




The authors thank Donniell Fishkind for his careful review of the manuscript. He did not receive compensation for his effort.


Dr. Pollack’s salary was supported by a career development award from the NIH National Cancer Institute and Office of Behavioral and Social Sciences Research (1K07CA151910-01A1). The funders had no role in the design and conduct off the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.

Conflict of Interest

This work was performed with support by faculty and staff at The Johns Hopkins University, where the ACG method was developed and is maintained. The Johns Hopkins University holds the copyright to the ACG software. To help support research and development, The Johns Hopkins University receives royalties from health plans and other organizations that use the ACG software. The authors declare that they do not have a conflict of interest.

Supplementary material

11606_2012_2104_MOESM1_ESM.docx (48 kb)
ESM 1 (DOCX 47 kb)


  1. 1.
    Institute of Medicine. Priority Areas for National Action: Transforming Health Care Quality. Washington, DC: National Academies Press; 2003.Google Scholar
  2. 2.
    National Priorities Partnership. National Priorities and Goals: Aligning Our Efforts to Transform America's Healthcare. Washington, DC: National Quality Forum; 2008:
  3. 3.
    Report to Congress. National Strategy for Quality Improvement in Health Care. Washington, DC: U.S. Department of Health and Human Services; 2011.Google Scholar
  4. 4.
    Miller HD. From volume to value: better ways to pay for health care. Health Aff. 2009;28:1418–1428.CrossRefGoogle Scholar
  5. 5.
    Rittenhouse DR, Shortell SM, Fisher E. Primary care and accountable care–two essential elements of delivery-system reform. N Engl J Med. 2009;361:2301–2303.PubMedCrossRefGoogle Scholar
  6. 6.
    Fisher ES, McClellan MB, Bertko J, et al. Fostering accountable health care: moving forward in Medicare. Health Aff. 2009;28(2):w219–w231.CrossRefGoogle Scholar
  7. 7.
    Rosenthal MB. Beyond pay for performance–emerging models of provider-payment reform. N Engl J Med. 2008;359:1197–1200.PubMedCrossRefGoogle Scholar
  8. 8.
    National Quality Forum, NQF-Endorsed Definition and Framework for Measuring Care Coordination,, Accessed April 24, 2012.
  9. 9.
    McDonald K, Schultz E, Albin L, et al. Care Coordination Measures Atlas. Vol No. 11-0023-EF. Rockville, MD: Agency for Healthcare Research and Quality; 2011: Accessed April 24, 2012.
  10. 10.
    Saultz JW. Defining and measuring interpersonal continuity of care. Ann Fam Med. 2003;1:134–143.PubMedCrossRefGoogle Scholar
  11. 11.
    Bice TW, Boxerman SB. A quantitative measure of continuity of care. Med Care. 1977;15:347–349.PubMedCrossRefGoogle Scholar
  12. 12.
    Jee SH, Cabana MD. Indices for continuity of care: a systematic review of the literature. Med Care Res Rev. 2006;63:158–188.PubMedCrossRefGoogle Scholar
  13. 13.
    Barnett ML, Landon BE, O'Malley AJ, Keating NL, Christakis NA. Mapping physician networks with self-reported and administrative data. Health Serv Res. 2011;46:1592–1609.PubMedCrossRefGoogle Scholar
  14. 14.
    Luke DA, Harris JK. Network analysis in public health: history, methods, and applications. Ann Rev Pub Health. 2007;28:69–93.CrossRefGoogle Scholar
  15. 15.
    Wasserman S, Faust K. Social Network Analysis: Methods and Applications. New York: Cambridge University Press; 1999.Google Scholar
  16. 16.
    Smith KP, Christakis NA. Social networks and health. Ann Rev Sociol. 2008;34:405–429.CrossRefGoogle Scholar
  17. 17.
    2010 National Healthcare Quality Report. 2010; Accessed April 24, 2012.
  18. 18.
    The Johns Hopkins ACG System Reference Manual Version 9.0. 2009; Accessed April 24, 2012.
  19. 19.
    Csardi G, Nepusz T. The igraph software package for complex network research. Paper presented at: International Conference on Complex Systems 2006; Boston, MA.Google Scholar
  20. 20.
    Weiner JP, Starfield BH, Steinwachs DM, Mumford LM. Development and application of a population-oriented measure of ambulatory care case-mix. Med Care. 1991;29:452–472.PubMedCrossRefGoogle Scholar
  21. 21.
    Starfield B, Shi L, Macinko J. Contribution of primary care to health systems and health. Milbank Q. 2005;83:457–502.PubMedCrossRefGoogle Scholar
  22. 22.
    Haggerty JL, Reid RJ, Freeman GK, Starfield BH, Adair CE, McKendry R. Continuity of care: a multidisciplinary review. Br Med J. 2003;327:1219–1221.CrossRefGoogle Scholar
  23. 23.
    Foy R, Hempel S, Rubenstein L, et al. Meta-analysis: effect of interactive communication between collaborating primary care physicians and specialists. Ann Intern Med. 2010;152:247–258.PubMedGoogle Scholar
  24. 24.
    O'Malley AS, Reschovsky JD. Referral and consultation communication between primary care and specialist physicians. Arch Intern Med. 2011;171:56–65.PubMedCrossRefGoogle Scholar
  25. 25.
    Chen AH, Kushel MB, Grumbach K, Yee HF. A safety-net systems gains efficiencies through 'eReferrals' to specialists. Health Aff. 2010;29:969–971.CrossRefGoogle Scholar
  26. 26.
    Kim Y, Chen AH, Keith E, Yee HF, Kushel MB. Not perfect, but better: primary care providers' experiences with electronic referrals in a safety net health system. J Gen Intern Med. 2009;24:614–619.PubMedCrossRefGoogle Scholar
  27. 27.
    Pham HH, O'Malley AS, Bach PB, Saiontz-Martinez C, Schrag D. Primary care physicians' links to other physicians through Medicare patients: the scope of care coordination. Ann Intern Med. 2009;150(4):236–242.PubMedGoogle Scholar
  28. 28.
    Pham HH, Schrag D, O'Malley AS, Wu B, Bach PB. Care patterns in Medicare and their implications for pay for performance. N Engl J Med. 2007;356(11):1130–1139.PubMedCrossRefGoogle Scholar
  29. 29.
    Bynum JPW, Bernal-Delgado E, Gottlieb D, Fisher E. Assigning ambulatory patients and their physicians to hospitals: a method for obtaining population-based provider performance measurements. Health Serv Res. 2007;42:45–62.PubMedCrossRefGoogle Scholar
  30. 30.
    Liebhaber A, Grossman JM. Physicians Moving to Mid-Sized, Single-Specialty Practices. Tracking Report No.18. 2007. Accessed April 24, 2012.
  31. 31.
    Singer SJ, Burgers J, Friedberg M, Rosenthal MB, Leape L, Schneider E. Defining and measuring integrated patient care: promoting the next frontier in health care delivery. Med Care Res Rev. 2011;68:112–127.PubMedCrossRefGoogle Scholar
  32. 32.
    Iezzoni LI. Assessing quality using administrative data. Ann Intern Med. 1997;127:666–674.PubMedGoogle Scholar

Copyright information

© Society of General Internal Medicine 2012

Authors and Affiliations

  • Craig Evan Pollack
    • 1
    • 2
  • Gary E. Weissman
    • 3
  • Klaus W. Lemke
    • 2
  • Peter S. Hussey
    • 4
  • Jonathan P. Weiner
    • 2
  1. 1.Johns Hopkins University School of MedicineBaltimoreUSA
  2. 2.Johns Hopkins Bloomberg School of Public HealthBaltimoreUSA
  3. 3.Internal Medicine Residency ProgramHospital of the University of PennsylvaniaPhiladelphiaUSA
  4. 4.RAND CorporationArlingtonUSA

Personalised recommendations