Search tips
Search criteria 


Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
JAMA. Author manuscript; available in PMC 2009 November 3.
Published in final edited form as:
PMCID: PMC2771916

Continuity of outpatient and inpatient care for hospitalized older adults

Gulshan Sharma, MD, MPH,1,3 Kathlyn E. Fletcher, MD MA,4 Dong Zhang, PhD,3 Yong-Fang Kuo, PhD,2,3 Jean L. Freeman, PhD,2,3 and James S. Goodwin, MD2,3



Little is known about the extent of continuity of care across the transition from outpatient care to hospitalization.


To describe continuity of care in older hospitalized patients, its change over time, and factors associated with discontinuity.

Design, Setting and Participants

Retrospective cohort study of hospital admissions from a 5% national sample of Medicare patients between1996 and 2006 (n=3,020,770).

Main Outcome Measures

Percent of hospitalized patients who were seen while hospitalized by any outpatient physician they had seen in the year prior to hospitalization (Continuity with any outpatient physician) or by their primary care physician (Continuity with a PCP).


In 1996, 50.5% (95% CI: 50.3% – 50.7%, n=125,789) of hospitalized patients saw at least one physician that they had seen in an outpatient setting in the prior year, whereas 44.3% (95% CI: 44.1% – 44.6%, n=58,046) of patients with an identifiable PCP saw that physician while hospitalized. These percentages had dropped to 39.8% (95% CI: 39.6%–40.0%, n=99,463) and 31.9% (95% CI: 31.6%–32.1%, n=47,761), respectively, by 2006. Greater absolute declines in continuity with any outpatient physician from 1996 to 2006 occurred in patients admitted on weekends (13.9%, 95% CI: 12.9%– 14.7%), those living in large metropolitan areas (11.7%, 95% CI: 11.1% – 12.3%) and in New England (16.2%, 95% CI: 14.4% – 18.0%). In multivariable, multilevel models, increasing involvement of hospitalists was associated with approximately one third of the decrease in continuity of care from 1996 to 2006.


Between 1996 and 2006, physician continuity from outpatient to inpatient settings declined in the Medicare population.


Continuity of care is a defining attribute of primary care and a core element of the Institute of Medicine definition of primary care1. Continuity is generally recognized to have three dimensions: continuity in information, in management and in the physician-patient relationship 2, 3. Relationship continuity is the ongoing interaction of a patient with one physician, which results in increased knowledge of patient preferences, better communication, and improved trust 4, 5. Guthrie and colleagues have argued that relationship continuity is especially important for older patients, because of the greater likelihood of multiple chronic conditions that benefit from informed management and shared decision making 6.

Almost all current research on continuity of care focuses on relationship continuity in outpatient settings. Such outpatient continuity has shown to be associated with improved patient satisfaction 35, 710, increased use of appropriate preventive health services 1115, greater medication compliance 16, lower hospitalization rates 1719, more appropriate end of life care 2022, and lower cost 23.

One aspect that has received relatively less attention is continuity of care across transitions: from community to hospital, from hospital to nursing home, etc. Such transitions threaten all aspects of continuity: information, management, and relationships 2426.

In this report we examine relationship continuity of care across the transition from community to hospitalization. We hypothesized that outpatient to inpatient continuity with hospitalized older adults declined between 1996 and 2006, and that the decline was greater in academic hospitals. We used two measures of continuity, one broad and the other narrowly defined. The broad measure defined continuity as a hospitalized patient seeing any physician that they had seen in an outpatient setting at least once in the prior year. The narrow measure was restricted to patients with identified primary care physicians (PCPs), and whether those PCPs saw the patient in the hospital.


Study Design

We conducted a retrospective cohort study using enrollment and claims data for a 5% national sample of Medicare beneficiaries 27. The Centers for Medicare and Medicaid Services (CMS) selected these beneficiaries based on the 8th and 9th digits (05, 20, 45, 70, 95) of their Health Insurance Claim number. Data files were constructed to include their demographic and enrollment information (Denominator File) and claims for hospital stays (MEDPAR File) and physician services (Carrier Claims File) 28. Characteristics of the hospitals were included in annual Provide of Services (POS) files 29.

Our study cohort consisted of all 5,487,771 hospital admissions from 1996 to 2006 for the 5% sample of Medicare beneficiaries older than 66 years of age. Excluded were admissions involving patients enrolled in HMOs or those who did not have Medicare Part A and B for the entire year prior to the admission (n=408,175). Patients with more than 20 admissions during the study period (n=173,072 admissions) were considered outliers (exceeding the 99th percentile) and were excluded. Also excluded were 11,671 admissions which could not be linked to POS files, resulting in 4,894,853 admissions. For patients with >1 admission in a given year, we randomly selected one admission per patient per year, resulting in 3,020,770 admissions for the analyses in this study.


Patient Characteristics

Medicare enrollment files were used to categorize patients by age, gender, and ethnicity. Race/ethnicity is self reported during the initial enrollment with the Social Security Administration (SSA) 30. A Medicaid indicator (state buy-in coverage) in the Denominator File was used as a proxy of low socioeconomic status. This variable indicates whether the beneficiary applied for eligibility and met the low income requirement for Medicaid 31. Distance between the hospital and the patient's residence was calculated using zip codes 32.

Hospital Admission Characteristics

Characteristics of the admission-including origin of the admission (via the emergency department vs. other), day admitted (weekend vs. weekday), and discharge diagnosis-related group (DRG), were obtained from the MEDPAR files. DRGs were classified as medical or surgical (see footnote to Table1).

Table 1
Percentage of hospitalized Medicare patients experiencing outpatient to inpatient continuity of care with any outpatient physician or with their PCP, stratified by patient and hospital characteristics.

Physician and Hospital Characteristics

The specialty code for physicians was based on the specialty designation in the Carrier Claims files33. Hospital information including zip code, metropolitan area size, state, total number of beds, type of hospital, and medical school affiliation were obtained from 2004 POS files. Metropolitan area size and total number of hospital beds were categorized by quartiles; states were grouped as census regions 34; type of hospital was categorized as non-profit, for profit, or public; and medical school affiliation was categorized as none, minor, or major 35.

Outpatient Physicians

Outpatient physicians were identified as any physician who had billed the hospitalized patient for at least one outpatient E&M code in the prior year. Of the 3,020,770 admissions studied, 2,759,795 (91.4%) had at least one outpatient physician. American Medical Association (AMA) Common Procedural Terminology (CPT) evaluation and management (E&M) codes 99201 to 99205 (new patient evaluation) and 99211 to 99215 (established patient follow up) were used to establish outpatient visits.

Primary Care Physician (PCP)

There is no agreed-upon algorithm to identify PCPs using administrative data 3642. We defined PCPs as a general practitioner, family physician, general internist, or a geriatrician who had billed an outpatient E&M code for the patient on three or more occasions in the year prior to the hospitalization. This definition has 76% concordance with the patient’s self identified PCP 42.

Outpatient to inpatient Continuity of Care

For most of the analyses we assessed outpatient to inpatient continuity in two ways. In one, we identified all hospitalizations in which the patient had seen (been billed by) a physician in an outpatient setting at least once in the year prior to admission. Among these hospitalizations (n= 2,759,795), we determined what percent were associated with an E&M charge during the hospital stay, by any physician who had billed for outpatient services in the prior year. This was termed “continuity with any outpatient physician.”

We also identified all hospitalizations in which the patient had an identifiable PCP, defined as above (n=1,547,513), and determined in what percent of those hospitalizations was the patient seen by their PCP. This was termed as “continuity with a PCP.” Inpatient claims were identified using AMA- CPT E&M codes 99221 to 99223 (initial hospital visit), 99251 to 99255 (inpatient consultation) and 99231 to 99233 (subsequent hospital visit).

We also explored different definitions of continuity. Instead of using an outpatient charge in the one year prior to the admission to establish the relationship, we expanded to two years and included physicians who had seen the patient either in an outpatient or inpatient setting during that time. For this analysis, our study cohort was limited to patients aged 67 and older (two years from enrollment age of 65 years) and hospitalized in 2006.


As previously described 43, we defined hospitalists as general internal medicine physicians who derive 90% or more of their Medicare claims for Evaluation and Management services (E&M) from care provided to hospitalized patients. If a patient had an inpatient E&M claim by a hospitalist physician during the hospitalization, then he/she was considered to have been cared for by a hospitalist physician.

The study was approved by the University of Texas Medical Branch Institutional Review Board.

Statistical Analyses

The proportions of admissions experiencing continuity of care with any outpatient physician or with their PCP were calculated, then stratified by selected patient and hospital characteristics. Linear trends in continuity were assessed by the Cochran-Armitage trend test. Three hierarchical generalized linear models (HGLM) with a logistic link, adjusting for clustering of admissions (level 1) within hospitals (level 2), were built for the outcome of continuity with any physician. In the first model, only admission year was included. Both patient characteristics (including age, gender, ethnicity, socio- economic status, emergency admission, weekend admission, DRG groups, distance from hospitals and comorbidity) and hospital characteristics (including region, metropolitan size, medical school affiliation, type of hospital, and hospital size) were added to the second model. In the third model, whether the patient was cared for by a hospitalist during the hospitalization was added. The mediating effect of hospitalist care on the association between admission year and continuity of care was evaluated by the method of Sobel 44. Finally, two pre-specified two-way interactions – admission year and medical school affiliation, and hospitalist care and medical school affiliation – were added to Model 2. All analyses were performed with SAS version 9.1 (SAS Inc., Cary, NC). The SAS GLIMMIX procedure was used to conduct multilevel analyses.

All reported p-values are two-sided and p<0.05 was considered statistically significant. The actual sample of 3,020,770 is overpowered for the analyses and likely to detect small differences which are statistically significant. Thus, the interpretation of analyses depends more on the magnitude of differences than on their statistical significance.


In 1996 through 2006, 45.2% (95% CI: 45.1% – 45.3%, n=1,246,201) of hospitalized patients received care during hospitalization by a physician who had seen them at least once as an outpatient in the prior year, while 38.0%( 95% CI:37.9% – 38.1%, n=587,269) of hospitalized patients with an identified PCP received care from that PCP during hospitalization.

Table 1 presents the percentage of the study sample from 1996–2006 seen during hospitalization by any physician they had seen as an outpatient in the prior year, or by their PCP, stratified by patient and hospital characteristics. Older patients, those with multiple comorbidities, those admitted through the emergency room, with medical (vs. surgical) diagnoses, living closer to the hospital, in smaller metropolitan areas or hospitalized in community hospitals were more likely to have continuity with any outpatient physician or with their PCP. There was also geographic variation in continuity of care, with the Rocky Mountain region having the lowest continuity.

Figure 1 presents the percentage of patients experiencing outpatient to inpatient continuity of care with any outpatient physician, or with their PCP, by year of hospitalization. Outpatient to inpatient continuity with any outpatient physician declined from 50.5% (95% CI: 50.3% – 50.7%, n=125,789) in 1996 to 39.8% (95% CI: 39.6%-40.0%, n=99,463) in 2006 (p<.001). Similarly, outpatient to inpatient continuity with a PCP declined from 44.3% (95% CI: 44.1% – 44.6%, n=58,046) in 1996 to 31.9% (31.6% – 32.1%, n=47,761) in 2006 (p<.001).

Figure 1
Percentage of pateints experiencing continuity with any outpatient physician or with their primary care physician (PCP) during hospitalization, 1996 through 2006.

Table 2 presents the absolute declines in continuity of care from 1996 to 2006 by patient and hospital characteristics. Declines in outpatient to inpatient continuity with any outpatient physician were seen in all strata, with greater absolute declines seen in those admitted on the weekend, those with medical diagnoses, and those living in larger metropolitan areas. Declines varied markedly by geographic area, with the largest absolute declines seen in New England. Similar declines were seen in continuity with a PCP.

Table 2
Percent of hospitalized patient experiencing continuity of care with any outpatient provider or thei PCP in 1996 and 2006, stratified by patient and hospital characteristics

Table 3 presents the results of multilevel multivariable analyses of factors associated with outpatient to inpatient continuity with any outpatient physician who saw the patient at least once in the year prior to hospitalization. As shown in Model 1, the odds of hospitalized patients receiving care from any outpatient physician declined by 3.9% (95% CI: 3.8% – 4.0%) per year from 1996 to 2006. This was not substantially changed (4.4%, 95% CI: 4.3% – 4.4%) after adjusting for other relevant factors in Model 2. Other factors associated with continuity were higher socioeconomic status, higher comorbidity, medical (vs. surgical) DRG, admission on a weekday, smaller metropolitan area, and care in a non-teaching, non-profit or smaller sized hospital. There were also substantial variations by geographic region.

Table 3
Multilevel multivariable analysis of odds of outpatient to inpatient continuity of care with any outpatient physician who saw the patient at least once in the year prior to hospitalization, 1996 to 2006.

In model 3 of Table 3 we included all the variables in model 2 and introduced whether the patient was cared for by a hospitalist during hospitalization. Adding this variable did not substantially alter the odds of continuity associated with the other variables, with the exception of admission year. The decline was 4.4% per year in Model 2, and reduced to 2.8% per year (95% CI: 2.7%-2.9%) when care by a hospitalist was added in Model 3.

We assessed whether changes in continuity of care varied between academic vs. community hospitals by testing two, two-way interactions in Model 3 of Table 3: the interaction of admission year and hospital teaching status (major medical school affiliation vs. none) and the interaction of hospitalist and hospital teaching status. Both interactions were significant. The odds of experiencing continuity of care declined more rapidly at major teaching hospitals, 4.4% per year (95% CI: 4.2% – 4.5% ) than at community hospitals, 2.3% per year (95% CI: 2.2% – 2.4%; P<0.001). Also, care by a hospitalist was associated with a 65.4% (95% CI: 65.0% – 65.9%) reduction in odds of continuity of care at community hospitals vs. a 53.4% (95% CI: 52.5% – 54.4%) reduction in major teaching hospitals (P<0.001). We also performed the analyses in Table 3 with the outcome of continuity with a PCP (data not shown). The results were similar to those presented for continuity with any outpatient physician.

Finally, we assessed the percentage of patients hospitalized in 2006 who were cared for in the hospital by any physician who had provided care for them in the prior two years, whether in an inpatient or outpatient setting. Using this definition, 47.7% of patients hospitalized in 2006 experienced continuity of care.


Our results showed that the proportion of patients experiencing continuity between outpatient and inpatient settings declined substantially from 1996 to 2006. By 2006 only 39.8% received care from any physician they had seen at least once in an outpatient setting in the prior year, while 31.9% of hospitalized patients with an identifiable PCP received care from that PCP. Declines in continuity of care occurred in all areas of the country, in all types of hospitals, and for all diagnoses.

As expected, outpatient to inpatient continuity was considerably less common in academic than community hospitals. Also, the decline in continuity was steeper over time at academic hospitals. By 2006 only 21.2% of Medicare patients hospitalized at academic hospitals saw their PCPs, compared to 36.8% of patients at community hospitals.

About one third of the decline in continuity from 1996 to 2006 was associated with growth in hospitalist activity, and there is a rough correspondence of regions of the country with the biggest decreases in continuity and those with the greatest increases in hospitalist activity 43.

Maintenance of continuity of care is well recognized as a challenge for hospitalist care. Medicare allows reimbursement for only one generalist physician for concurrent care in the hospital45, so there is a financial disincentive for outpatient physicians to follow their patients in the hospital if they are receiving hospitalist care. Problems with information transfer at admission and unclear responsibility after discharge have been identified 26, with direct communication between the hospitalist and PCP occurring in less than 20% of cases 46.

On the other hand, there are clear benefits to the hospitalist system, including greater efficiency in both hospitalized 47 and outpatient care 48. It is also important to note that the increase in hospitalist care was related to only about a third of the decrease in continuity over the 1996–2006 period. None of the other patient or hospital attributes included in Table 3 were strongly associated with the decline in continuity. We assume many organizational changes, of which the hospitalist movement is only the most visible, contributed to the decline, including increasing participation in group practices. Shared call schedules as well as improvements in communication, such as electronic medical records, may reduce the need for a patient’s outpatient physician to actively participate in their inpatient care.

Patients with comorbid illnesses and vey old patienst were more likely to have continuity with their outpatient physicians and with their PCP during hospitalization. This would seem an appropriate adjustment in a situation where continuity may be more important6.

The limitations of this study are those inherent in analyses of administrative databases. For example, our method of assessing continuity was by determining whether a patient's outpatient physician submitted a charge to Medicare for evaluation and management services while the patient was hospitalized. It is likely that some physicians visited their patients without billing. However our estimate of continuity with a PCP was close to that obtained in a recent survey of 556 PCPs in California, where 34% stated that they usually or always visited their hospitalized patients 49. A number of instruments using administrative data 17, 5055 or patient questionnaires 1113, 5658 have been developed to assess relationship continuity. Rodriguez et al. 59 assessed the concordance of patient–reported and administratively derived measures of continuity in a sample of 15,126 patients and concluded that administratively derived measures are less susceptible to bias.

A second limitation of our study is that we only examined changes in relationship continuity and did not have information on other domains of continuity, such as information or management continuity. A hospitalized patient may experience continuity in information without relationship continuity. For example, the patient might be followed in the hospital by a group practice associate of their PCP. Plus, the growing use of electronic health record should promote informational continuity 6062. In the era of electronic communication, physicians and patients are more likely to communicate via cell phones or emails to relay information. This is not captured in the administrative datasets, which may lead to an overestimation of the decline in continuity with a PCP.

A third limitation is that our study used Medicare data, and so our findings may not generalize to non-Medicare patients. In addition, the findings may not be generalizeable to Medicare beneficiaries enrolled in managed care plans or those without Medicare part B coverage. A change in HMO enrollments during the study period might have affected the analysis of the time trends in outpatient to inpatient continuity. Another limitation is the algorithm used to identify PCPs, which required three outpatient visits in the prior year and thus may have missed many PCPs. A recent report showed a 76% concordance between this algorithm and self report by patients 42. Moreover, the absolute declines in outpatient to inpatient continuity over time were similar whether we looked at continuity with a PCP or with any outpatient physician who saw the patient at least once in the prior year.

Our work suggests that a majority of older hospitalized patients are not seen by any physician that they had seen previously. A recent study of patients hospitalized at an academic hospital found that 75% were unable to name any physician participating in their care 63. Hospitalization is a stressful time, and is also the occasion for serious and sometimes difficult decisions regarding different treatments. One might expect that the ongoing participation of a physician well known to the patient might lead to decision making that reflects the patient’s values. For example, patients hospitalized with advanced lung cancer in the last six months of life are less likely to spend time in an ICU if they are cared for by their outpatient physician during that hospitalization 22.

In summary, continuity of care from the outpatient to hospital setting is low and is declining. Only a part of this decrease would appear to be related to the growth of the hospitalist model. Future research should explore whether the lack of continuity contributes to suboptimal care, and also whether interventions might ameliorate any detrimental effects of discontinuities in care.


This work was supported by grant P50 CA 105631 from the National Cancer Institute, K-08 AG 031583 and P60 AG 17231 from the National Institute on Aging. Dong D. Zhang Ph.D. had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Dong Zhang Ph.D. and Yong-Fang Kuo Ph.D. performed and are responsible for the statistical analysis for this study. The funding agencies has no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript


Financial Disclosure: None of the authors has a financial relationship with a commercial entity that has an interest in the content of this manuscript.

Reference List

1. Committee on the future of primary care. Institue of Medicine: National Academy of Sciences. 1st ed. Washington, DC: 1996. Primary Care. America's health in new era. ed.
2. Haggerty JL, Reid RJ, Freeman GK, Starfield BH, Adair CE, McKendry R. Continuity of care: a multidisciplinary review. BMJ. 2003 November 22;327(7425):1219–1221. [PMC free article] [PubMed]
3. Saultz JW, Albedaiwi W. Interpersonal continuity of care and patient satisfaction: a critical review. Ann Fam Med. 2004 September;2(5):445–451. [PubMed]
4. Mainous AG, III, Baker R, Love MM, Gray DP, Gill JM. Continuity of care and trust in one's physician: evidence from primary care in the United States and the United Kingdom. Fam Med. 2001 January;33(1):22–27. [PubMed]
5. Mainous AG, III, Goodwin MA, Stange KC. Patient-physician shared experiences and value patients place on continuity of care. Ann Fam Med. 2004 September;2(5):452–454. [PubMed]
6. Guthrie B, Saultz JW, Freeman GK, Haggerty JL. Continuity of care matters. BMJ. 2008;337:a867. [PubMed]
7. Love MM, Mainous AG, III, Talbert JC, Hager GL. Continuity of care and the physician-patient relationship: the importance of continuity for adult patients with asthma. J Fam Pract. 2000 November;49(11):998–1004. [PubMed]
8. Mainous AG, III, Kern D, Hainer B, Kneuper-Hall R, Stephens J, Geesey ME. The relationship between continuity of care and trust with stage of cancer at diagnosis. Fam Med. 2004 January;36(1):35–39. [PubMed]
9. Shear CL, Gipe BT, Mattheis JK, Levy MR. Provider continuity and quality of medical care. A retrospective analysis of prenatal and perinatal outcome. Med Care. 1983 December;21(12):1204–1210. [PubMed]
10. Stokes T, Tarrant C, Mainous AG, III, Schers H, Freeman G, Baker R. Continuity of care: is the personal doctor still important? A survey of general practitioners and family physicians in England and Wales, the United States, and The Netherlands. Ann Fam Med. 2005 July;3(4):353–359. [PubMed]
11. Ettner SL. The relationship between continuity of care and the health behaviors of patients: does having a usual physician make a difference? Med Care. 1999 June;37(6):547–555. [PubMed]
12. O'Malley AS, Mandelblatt J, Gold K, Cagney KA, Kerner J. Continuity of care and the use of breast and cervical cancer screening services in a multiethnic community. Arch Intern Med. 1997 July 14;157(13):1462–1470. [PubMed]
13. Ettner SL. The timing of preventive services for women and children: the effect of having a usual source of care. Am J Public Health. 1996 December;86(12):1748–1754. [PubMed]
14. Parchman ML, Burge SK. The patient-physician relationship, primary care attributes, and preventive services. Fam Med. 2004 January;36(1):22–27. [PubMed]
15. Atlas SJ, Grant RW, Ferris TG, Chang Y, Barry MJ. Patient-physician connectedness and quality of primary care. Ann Intern Med. 2009 March 3;150(5):325–335. [PMC free article] [PubMed]
16. Kerse N, Buetow S, Mainous AG, III, Young G, Coster G, Arroll B. Physician-patient relationship and medication compliance: a primary care investigation. Ann Fam Med. 2004 September;2(5):455–461. [PubMed]
17. Christakis DA, Mell L, Koepsell TD, Zimmerman FJ, Connell FA. Association of lower continuity of care with greater risk of emergency department use and hospitalization in children. Pediatrics. 2001 March;107(3):524–529. [PubMed]
18. Gill JM, Mainous AG., III The role of provider continuity in preventing hospitalizations. Arch Fam Med. 1998 July;7(4):352–357. [PubMed]
19. Mainous AG, III, Gill JM. The importance of continuity of care in the likelihood of future hospitalization: is site of care equivalent to a primary clinician? Am J Public Health. 1998 October;88(10):1539–1541. [PubMed]
20. Burge F, Lawson B, Johnston G, Cummings I. Primary care continuity and location of death for those with cancer. J Palliat Med. 2003 December;6(6):911–918. [PubMed]
21. Burge F, Lawson B, Johnston G. Family physician continuity of care and emergency department use in end-of-life cancer care. Med Care. 2003 August;41(8):992–1001. [PubMed]
22. Sharma G, Freeman J, Zhang D, Goodwin JS. Continuity of care and intensive care unit use at the end of life. Arch Intern Med. 2009 January 12;169(1):81–86. [PMC free article] [PubMed]
23. Weiss LJ, Blustein J. Faithful patients: the effect of long-term physician-patient relationships on the costs and use of health care by older Americans. Am J Public Health. 1996 December;86(12):1742–1747. [PubMed]
24. Coleman EA, Min SJ, Chomiak A, Kramer AM. Posthospital care transitions: patterns, complications, and risk identification. Health Serv Res. 2004 October;39(5):1449–1465. [PMC free article] [PubMed]
25. Coleman EA, Berenson RA. Lost in transition: challenges and opportunities for improving the quality of transitional care. Ann Intern Med. 2004 Octobr 5;141(7):533–536. [PubMed]
26. Pham HH, Grossman JM, Cohen G, Bodenheimer T. Hospitalists and care transitions: the divorce of inpatient and outpatient care. Health Aff (Millwood ) 2008 September;27(5):1315–1327. [PubMed]
27. Centers for Medicare and Medicaid Services. Standard analytical files. 2009. [Accessed June1, 2008]. http://www cms hhs gov/IdentifiableDataFiles/02StandardAnalyticalFiles asp.
28. Research Data Assistance Center. Medicare datafiles descriptions. 2008. [Accessed June1, 2008]. http://www resdac umn edu/Medicare/file_descriptions asp.
29. Centers for Medicare and Medicaid Services. 2008. [Accessed June1, 2008]. http://www cms hhs gov/NonIdentifiableDataFiles/04_ProviderofServicesFile asp.
30. Arday SL, Arday DR, Monroe S, Zhang J. HCFA's racial and ethnic data: current accuracy and recent improvements. Health Care Financ Rev. 2000;21(4):107–116. [PubMed]
31. Bach PB, Guadagnoli E, Schrag D, Schussler N, Warren JL. Patient demographic and socioeconomic characteristics in the SEER-Medicare database application and limitations. Med Care. 2002;40:19–25. [PubMed]
32. Riall TS, Eschbach KA, Townsend CM, Jr, Nealon WH, Freeman JL, Goodwin JS. Trends and disparities in regionalization of pancreatic resection. J Gastrointest Surg. 2007 October;11(10):1242–1251. [PubMed]
33. Baldwin LM, Adamache W, Klabunde CN, Kenward K, Dahlman C, Warren L. Linking physician characteristics and medicare claims data: issues in data availability, quality, and measurement. Med Care. 2002 August;40(8 Suppl):IV-95. [PubMed]
35. Shahinian VB, Kuo YF, Freeman JL, Orihuela E, Goodwin JS. Characteristics of urologists predict the use of androgen deprivation therapy for prostate cancer. J Clin Oncol. 2007 December 1;25(34):5359–5365. [PMC free article] [PubMed]
36. Finison KS, Wellins CA, Wennberg DE, Lucas FL. Screening Mammography Rates by the Specialty of the Usual Care Physician. Effective Clinical Practice. 1999;2:120–125. [PubMed]
37. 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 March 15;356(11):1130–1139. [PubMed]
38. Rosenblatt RA, Hart LG, Baldwin LM, Chan L, Schneeweiss R. The generalist role of specialty physicians: is there a hidden system of primary care? JAMA. 1998 May 6;279(17):1364–1370. [PubMed]
39. Landon BE, Normand SL, Blumenthal D, Daley J. Physician clinical performance assessment: prospects and barriers. JAMA. 2003 September e;290(9):1183–1189. [PubMed]
40. Scholle SH, Roski J, Dunn DL, et al. Availability of data for measuring physician quality performance. Am J Manag Care. 2009 January;15(1):67–72. [PMC free article] [PubMed]
41. Atlas SJ, Chang Y, Lasko TA, Chueh HC, Grant RW, Barry MJ. Is this "my" patient? Development and validation of a predictive model to link patients to primary care providers. J Gen Intern Med. 2006 September;21(9):973–978. [PMC free article] [PubMed]
42. Shah BR, Hux JE, Laupacis A, Zinman B, Cauch-Dudek K, Booth GL. Administrative data algorithms can describe ambulatory physician utilization. Health Serv Res. 2007 August;42(4):1783–1796. [PMC free article] [PubMed]
43. Kuo Y-F, Sharma G, Freeman JL, Goodwin JS. Growth of General Internal Medicine Hospitalists Caring for Older adults in US Hospitals. N Engl J Med. 2009 (in press)
44. Sobel ME. Asymptotic Confidence Intervals for Indirect Effects in Structural Equation Models. Sociological Methodology. 1982;13:290–312.
45. Moore KJ. A refresher on Medicare and concurrent care. Fam Pract Manag. 2005 November;12(10):29–30. [PubMed]
46. Kripalani S, LeFevre F, Phillips CO, Williams MV, Basaviah P, Baker DW. Deficits in communication and information transfer between hospital-based and primary care physicians: implications for patient safety and continuity of care. JAMA. 2007 February 28;297(8):831–841. [PubMed]
47. Lindenauer PK, Rothberg MB, Pekow PS, Kenwood C, Benjamin EM, Auerbach AD. Outcomes of care by hospitalists, general internists, and family physicians. N Engl J Med. 2007 December 20;357(25):2589–2600. [PubMed]
48. Freese RB. The Park Nicollet experience in establishing a hospitalist system. Ann Intern Med. 1999 February 16;130(4 Pt 2):350–354. [PubMed]
49. Pantilat SZ, Lindenauer PK, Katz PP, Wachter RM. Primary care physician attitudes regarding communication with hospitalists. Am J Med. 2001 December 21;111(9B):15S–20S. [PubMed]
50. Ejlertsson G, Berg S. Continuity-of-care measures. An analytic and empirical comparison. Med Care. 1984 March;22(3):231–239. [PubMed]
51. Citro R, Ghosh S, Churgin PG. A fundamental metric for continuity of care: modeling and performance evaluation. IEEE Trans Inf Technol Biomed. 1997 September;1(3):189–204. [PubMed]
52. Bice TW, Boxerman SB. A quantitative measure of continuity of care. Med Care. 1977 April;15(4):347–349. [PubMed]
53. Breslau N, Haug MR. Service delivery structure and continuity of care: a case study of a pediatric practice in process of reorganization. J Health Soc Behav. 1976 December;17(4):339–352. [PubMed]
54. Smedby O, Eklund G, Eriksson EA, Smedby B. Measures of continuity of care: A register-based correlation study. Med Care. 1986 June;24(6):511–518. [PubMed]
55. Steinwachs DM. Measuring provider continuity in ambulatory care: an assessment of alternative approaches. Med Care. 1979 June;17(6):551–565. [PubMed]
56. Gallagher TC, Geling O, Comite F. Use of multiple providers for regular care and women's receipt of hormone replacement therapy counseling. Med Care. 2001 October;39(10):1086–1096. [PubMed]
57. Lambrew JM, DeFriese GH, Carey TS, Ricketts TC, Biddle AK. The effects of having a regular doctor on access to primary care. Med Care. 1996 February;34(2):138–151. [PubMed]
58. Slater B, Cornforth J. Continuity of care on admission to hospital: an audit of Airedale NHS Trust's transfer policy. Int J Health Care Qual Assur. 1996;9(1):34–37. [PubMed]
59. Rodriguez HP, Marshall RE, Rogers WH, Safran DG. Primary care physician visit continuity: a comparison of patient-reported and administratively derived measures. J Gen Intern Med. 2008 September;23(9):1499–1502. [PMC free article] [PubMed]
60. Bates DW. Physicians and ambulatory electronic health records. Health Aff (Millwood ) 2005 September;24(5):1180–1189. [PubMed]
61. Weiner M, Callahan CM, Tierney WM, et al. Using information technology to improve the health care of older adults. Ann Intern Med. 2003 September 2;139(5 Pt 2):430–436. [PubMed]
62. Weiner M, Biondich P. The influence of information technology on patient-physician relationships. J Gen Intern Med. 2006 January;21 Suppl 1:S35–S39. [PMC free article] [PubMed]
63. Arora V, Gangireddy S, Mehrotra A, Ginde R, Tormey M, Meltzer D. Ability of hospitalized patients to identify their in-hospital physicians. Arch Intern Med. 2009 January 26;169(2):199–201. [PubMed]