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September 2011

Anne Elixhauser, Ph.D., David H. Au, M.D., M.S., Jennifer Podulka, M.P.Aff.



Introduction

High rates of hospital readmissions and unexplained variation in those rates may indicate problems in transitions of care and outpatient management following discharge. While some readmissions may be unavoidable, reducing hospital readmissions has been an objective of the Affordable Care Act and accountable care organizations. Improving the quality of care including care transitions at the time of hospital discharge may result in fewer hospital readmissions and associated costs. Examining characteristics that explain variability in readmission rates can help to identify opportunities for targeted interventions for patients with common high risk conditions such as chronic obstructive pulmonary disease (COPD).^1,2,3

Based on data from 2003-2004, 22.6 percent of fee-for-service Medicare beneficiaries admitted to the hospital for COPD were readmitted within 30 days.⁴ This Statistical Brief presents data on hospital readmissions within 30 days following an initial hospital stay for COPD among patients 40 years old and older in 15 states in 2008.⁵ The 15 states are geographically dispersed and account for 42 percent of the total U.S. resident population.

For this Statistical Brief, the initial—or index—admission occurred between January and November of 2008. The 30-day readmission rate is defined as any repeat admission within 30 days after being discharged alive from an index hospital stay divided by the total number of index admissions between January and November 2008.⁶ An individual patient can have multiple index admissions during this observation period. More details on how readmissions were calculated are available under "Definitions".

In all cases COPD was the principal diagnosis during the index stay, but three alternative definitions of readmissions were examined—COPD was the principal diagnosis on the readmission, COPD was any diagnosis, and COPD did not appear as a diagnosis on the subsequent stay. Differences in 30-day readmission rates by patient age, sex, income, and race are presented, along with information on costs of index admissions and readmissions.⁷

All numbers noted in the text and included in the tables are actual values, not estimates, as the data include a census of discharges, not a sample of discharges. In other words, we count the actual number of patients hospitalized for COPD in the 15 states and their actual readmissions. Because we are describing a population rather than a sample that represents an underlying population, there is no sampling error associated with the calculated values presented and significance testing is not necessary.⁸

Findings

In the 15 states examined here, there were 190,700 index admissions with COPD as the principal diagnosis among patient 40 years and older (table 1). Among these patients, 7.1 percent of index admissions were followed by at least one readmission within 30 days for a principal diagnosis of COPD. When COPD was listed as any diagnosis (principal or secondary) during a subsequent hospital stay, 30-day readmission rates were 17.3 percent. When all-cause 30-day readmissions were considered (including those with no COPD diagnosis on the subsequent admission), 20.5 percent of COPD index admissions were followed by a readmission within 30 days.

As shown in table 1, costs for readmissions were higher than costs for COPD index admissions.9 Index admissions cost an average of $7,100 compared to $8,400 for readmissions with COPD as the principal diagnosis, $10,900 readmissions when COPD was listed as any diagnosis, and $11,100 for all-cause readmissions. Compared with the index stay, readmissions for COPD as the principal diagnosis cost 18 percent more; while costs for other types of readmissions cost over 50 percent more than the index hospital stay.

30-day readmission rates by patient characteristics in 15 states, 2008
Table 2 provides 30-day readmission rates by patient characteristics. For readmissions in which COPD was the principal diagnosis, readmission rates were 15 percent higher among adults 40-64 years old (7.8 percent of index admissions were followed by at least one readmission within 30 days) than among the elderly (6.8 percent of index admissions were followed by at least one readmission). Thirty-day readmission rates were 13 percent higher among males (7.6 percent) compared to females (6.7 percent).

Among COPD patients residing in the lowest income areas, 7.8 percent of index admissions were followed by a readmission principally for COPD—about 22 percent higher than among patients from the highest income areas (6.4 percent readmitted).

For black patients, 8.0 percent of index admissions were followed by a readmission within 30-days principally for COPD—30 percent higher than among the groups with the lowest readmission rate, Hispanic patients and Asian and Pacific Islander patients (6.1 percent were readmitted for both groups).

Comparable patterns were seen for the alternative definitions of readmissions—for COPD as any diagnosis and for all-cause readmissions, except for age. In contrast to readmissions with COPD as the principal diagnosis where younger patients had 15 percent higher readmission rates, elderly patients had 10 percent higher readmission rates when COPD was any diagnosis and only 5 percent higher readmission rates for all-cause readmissions.

Under the alternative definitions of readmissions, males had 10-14 percent higher readmission rates than females, comparable to the differences seem for readmissions with COPD as the principal diagnosis.

Differences by median household income were much smaller—5-6 percent higher readmission rates for patients from the lowest income ZIP Codes, compared to 22 percent higher for readmissions with COPD as the principal diagnosis.

Differences by race were also less pronounced—13-20 percent higher readmission rates for blacks compared to Hispanics and Asian/Pacific Islanders, compared to 30 percent higher for readmissions with COPD as the principal diagnosis.

30-day readmission costs by patient characteristics in 15 states, 2008
Statewide area wage indexes were used to adjust costs to account for local differences in costs. This is especially important for comparisons by race/ethnicity because several high cost states contributed larger proportions of Hispanics and Asian/Pacific Islanders.

Costs were consistently higher for readmissions than for index stays (table 3). As described earlier, compared to the index stay, costs were 18 percent higher for readmissions with COPD as the principal diagnosis and more than 50 percent higher for other types of readmissions.

Costs were slightly lower for patients 40-64 years old than for patients 65 and older across all types of readmissions. The magnitude of difference between the cost of index admissions and readmissions was similar across all readmission types.

There were also small differences in the costs for readmissions by patient sex. Costs were slightly higher for male patients across all types of readmissions.

For both index admissions and readmissions, costs were consistently higher in higher income communities.

There were large differences in the costs of 30-day readmissions among COPD patients by race and ethnicity. For all three types of readmissions, the lowest cost readmissions were for white patients and the highest cost readmissions were for Asian and Pacific Islander patients. Readmissions among Asian and Pacific Islander patients cost between 32 and 38 percent more than readmissions among white patients. Much smaller differences were seen between the other subgroups.

Data Source

The estimates in this Statistical Brief are based upon data from the HCUP 2008 State Inpatient Databases for 15 states: Arkansas, California, Florida, Hawaii, Louisiana, Massachusetts, Missouri, Nebraska, New Hampshire, New York, South Carolina, Tennessee, Utah, Virginia, and Washington. These states were selected based on availability of synthetic patient-level identifiers that enabled tracking of patients across time.

Definitions

Readmission
The 30-day readmission rate is defined as any repeat admission within 30 days after being discharged alive from an index hospital stay (where COPD is the principal diagnosis) divided by the total number of index admissions between January and November 2008. In other words, once a patient is discharged from the hospital with a principal diagnosis of COPD, they are followed for 30 days in the data. If any readmission occurs during this time period, the patient is counted as having a readmission. No more than one readmission is counted within the 30-day period since the outcome measure assessed here is "percentage of patients who are readmitted".

Following the 30-day period, if a patient experiences another hospital stay with COPD as the principal diagnosis, it is counted as a second index admission, the 30-day follow-up period begins again, and another readmission can be counted in the 30-day window. Thus a single patient can be counted multiple times during the course of the January to November observation period. This method follows the approach described by Jencks et al. (2009).¹⁰

Discharges for patients who died during an index admission or whose index admission occurred in December of 2008 were also disqualified because they could not be followed for 30 days. If a patient was transferred to a different hospital on the same day or was transferred within the same hospital, the two events were combined as a single stay and the second event was not counted as a readmission. In other words, transfers were not considered a readmission. Multiple discharges that represented the transfer of a patient from one hospital to another, or from one unit of a hospital to another, were combined so that the second part of each "episode of care" was not counted as a readmission. If for the same person, one discharge ended on the same day as a second discharge started, the two discharge records were combined into a single "transfer" record. The combined transfer record retained the diagnoses from the second discharge and combined the length of stay and total hospital charges from the two discharges. The percentage of discharges that were considered transfers in each state ranged from 1.7 percent to 6.1 percent with an average of 2.9 percent.

Diagnoses
The principal diagnosis is that condition established after study to be chiefly responsible for the patient's admission to the hospital. Secondary diagnoses are concomitant conditions that coexist at the time of admission or that develop during the stay. All-listed diagnoses include the principal diagnosis plus these additional secondary conditions.

Types of hospitals included in HCUP
HCUP is based on data from community hospitals, defined as short-term, non-Federal, general and other hospitals, excluding hospital units of other institutions (e.g., prisons). HCUP data include OB-GYN, ENT, orthopedic, cancer, pediatric, public, and academic medical hospitals. Excluded are long-term care, rehabilitation, psychiatric, and alcoholism and chemical dependency hospitals. Please note, a discharge of this nature will be included in the SID if it occurred in a community hospital.

Costs
Total hospital costs tend to reflect the actual costs of production, while charges represent what the hospital billed for the case. Total hospital charges were converted to costs using HCUP cost-to-charge ratios based on hospital accounting reports from the Centers for Medicare & Medicaid Services (CMS).¹¹ For each hospital, a hospital-wide cost-to-charge ratio is used. For the purposes of this Statistical Brief, costs are reported to the nearest hundred. Statewide average area wage indexes weighted by bed size were used to adjust for local differences in costs.

About HCUP
HCUP is a family of powerful healthcare databases, software tools, and products for advancing research. Sponsored by the Agency for Healthcare Research and Quality (AHRQ), HCUP includes the largest all-payer encounter-level collection of longitudinal healthcare data (inpatient, ambulatory surgery, and emergency department) in the United States, beginning in 1988. HCUP is a Federal-State-Industry Partnership that brings together the data collection efforts of many organizations—such as State data organizations, hospital associations, private data organizations, and the Federal government—to create a national information resource.

HCUP would not be possible without the contributions of the following data collection Partners from across the United States:

Arizona Department of Health Services
Arkansas Department of Health
California Office of Statewide Health Planning and Development
Colorado Hospital Association
Connecticut Hospital Association
Florida Agency for Health Care Administration
Georgia Hospital Association
Hawaii Health Information Corporation
Illinois Department of Public Health
Indiana Hospital Association
Iowa Hospital Association
Kansas Hospital Association
Kentucky Cabinet for Health and Family Services
Louisiana Department of Health and Hospitals
Maine Health Data Organization
Maryland Health Services Cost Review Commission
Massachusetts Division of Health Care Finance and Policy
Michigan Health & Hospital Association
Minnesota Hospital Association
Missouri Hospital Industry Data Institute
Montana MHA — An Association of Montana Health Care Providers
Nebraska Hospital Association
Nevada Department of Health and Human Services
New Hampshire Department of Health & Human Services
New Jersey Department of Health and Senior Services
New Mexico Health Policy Commission
New York State Department of Health
North Carolina Department of Health and Human Services
Ohio Hospital Association
Oklahoma State Department of Health
Oregon Association of Hospitals and Health Systems
Pennsylvania Health Care Cost Containment Council
Rhode Island Department of Health
South Carolina State Budget & Control Board
South Dakota Association of Healthcare Organizations
Tennessee Hospital Association
Texas Department of State Health Services
Utah Department of Health
Vermont Association of Hospitals and Health Systems
Virginia Health Information
Washington State Department of Health
West Virginia Health Care Authority
Wisconsin Department of Health Services
Wyoming Hospital Association

About the SID

The HCUP State Inpatient Databases (SID) are hospital inpatient databases from data organizations participating in HCUP. The SID contains the universe of the inpatient discharge abstracts in the participating HCUP states, translated into a uniform format to facilitate multistate comparisons and analyses. Together, the SID encompasses 95 percent of all U.S. community hospital discharges in 2009. The SID can be used to investigate questions unique to one state; to compare data from two or more states; to conduct market area variation analyses; and to identify state-specific trends in inpatient care utilization, access, charges, and outcomes.

For More Information

For more information about HCUP, visit http://www.hcup-us.ahrq.gov.

For additional HCUP statistics, visit HCUPnet, our interactive query system, at www.hcup.ahrq.gov.

For information on other hospitalizations in the U.S., download HCUP Facts and Figures: Statistics on Hospital-Based Care in the United States in 2008, located at http://www.hcup-us.ahrq.gov/reports.jsp.

For more information on the design of the SID, more information on the HCUP Revisit Files, and methods to make inferences based on state databases, please refer to the following publications:

Introduction to the HCUP State Inpatient Databases. Online. June 2010. U.S. Agency for Healthcare Research and Quality. http://hcup-us.ahrq.gov/db/state/siddist/Introduction_to_SID.pdf

Overview of the HCUP Supplemental Files for Revisit Analyses available at http://www.hcup-us.ahrq.gov/toolssoftware/revisit/revisit.jsp.

Houchens R. Inferences with HCUP State Databases Final Report. HCUP Methods Series Report # 2010-05. Online October 12, 2010. U.S. Agency for Healthcare Research and Quality. Available: http://www.hcup-us.ahrq.gov/reports/methods/2010_05.pdf.

Suggested Citation

Elixhauser, A. (AHRQ), Au, D. (AHRQ), and Podulka, J. (Thomson Reuters). Readmissions for Chronic Obstructive Pulmonary Disease, 2008. HCUP Statistical Brief #121. September, 2011. Agency for Healthcare Research and Quality, Rockville, MD. http://www.hcup-us.ahrq.gov/reports/statbriefs/sb121.pdf

Acknowledgements

The authors would like to acknowledge Marguerite Barrett for her assistance on this analysis.

Dr. Au was supported through the Department of Veterans Affairs, VA Puget Sound Health Care System and Health Services Research and Development

Disclaimer: The views expressed represent those of the authors and do not necessarily represent the views of the Department of Veterans Affairs.

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AHRQ welcomes questions and comments from readers of this publication who are interested in obtaining more information about access, cost, use, financing, and quality of healthcare in the United States. We also invite you to tell us how you are using this Statistical Brief and other HCUP data and tools, and to share suggestions on how HCUP products might be enhanced to further meet your needs. Please e-mail us at hcup@ahrq.gov or send a letter to the address below:

Irene Fraser, Ph.D., Director
Center for Delivery, Organization, and Markets
Agency for Healthcare Research and Quality
540 Gaither Road
Rockville, MD 20850



¹ Westert G. P., Lagoe R. J., Keskimaki I., Leyland A., Murphy M. An international study of hospital readmissions and related utilization in Europe and the USA. Health Policy 2002; 61(3):269-278.
² Garcia-Aymerich J., Farrero E., Felez M. A., Izquierdo J., Marrades R. M., Anto J. M. Risk factors of readmission to hospital for a COPD exacerbation: a prospective study. Thorax 2003; 58:100-105.
³ Chen Y., Li Q., Johansen H. Age and sex variations in hospital readmissions for COPD associated with overall and cardiac comorbidity. International Journal of Tuberculosis and Lung Disease 2009; 13(3):394-399.
⁴ Jencks S. F., Williams M.V., Coleman E. A. Rehospitalizations among patients in the Medicare Fee-for-Service program. NEJM 2009; 360:1418-1428.
⁵ The 15 states are Arkansas, California, Florida, Hawaii, Louisiana, Massachusetts, Missouri, Nebraska, New Hampshire, New York, South Carolina, Tennessee, Utah, Virginia, and Washington. These states were selected based on availability of synthetic patient-level identifiers that enabled tracking of patients across time.
⁶ No more than one readmission is counted within the 30-day period
⁷ Patient race is reported for the 12 state databases that included data on race/ethnicity: Arkansas, California, Florida, Hawaii, Massachusetts, Missouri, New Hampshire, New York, South Carolina, Tennessee, Utah, and Virginia.
⁸ Houchens, R. Inferences with HCUP State Databases Final Report. HCUP Methods Series Report # 2010-05. Online October 12, 2010. U.S. Agency for Healthcare Research and Quality. Available: http://www.hcup-us.ahrq.gov/reports/methods/2010_05.pdf. Accessed on May 25, 2011.
⁹ Hospital costs are adjusted by the statewide mean area wage index weighted by bed size.
¹⁰ Jencks S. F., Williams M. V., Coleman E. A. Rehospitalizations among patients in the Medicare Fee-for-Service program. NEJM 2009; 360:1418-1428.
¹¹ HCUP Cost-to-Charge Ratio Files (CCR). Healthcare Cost and Utilization Project (HCUP). 2001-2008. U.S. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/state/costtocharge.jsp.