State Hospital Discharge Data

Uses for Asthma Hospitalization Surveillance

Asthma hospitalization data can be used to examine the statewide severity of asthma, both from the perspective of the community and from the perspective of individual persons.  Some of the questions these data can answer are:

Q  What are the numbers and rates of hospitalizations for asthma?

Q  Are the asthma hospitalization rates higher than the national rate or the HP2020 objectives?

Q  Do asthma hospitalization rates vary by age, sex, race, and/or geography?

Q  What are the yearly trends in asthma hospitalization rates?

History of Hospital Discharge Data Collection at the State and Local Level

State-specific hospital discharge databases are currently available in 48 states¹. These data are collected for billing and other administrative purposes (e.g., the Uniform Hospital Discharge Data Set or Uniform Bill 92), rather than surveillance purposes. The data variables and the number of years that the data are available vary from state to state.

Source of Data (How to Access the Data)

Ownership of these data also varies by state. In some states, the state health department has the legislative authority to collect the data; in other states data are collected and maintained by a private organization that has agreements to share the data with the state health department. In some states, patient, provider, and hospital identifiers are not included in shared data sets².  A list of state hospital associations can be found on the website of the American Hospital Association at http://www.aha.org/about/srmassoc/index.shtmlexternal icon.  If state level data are not accessible, local health departments may be able to obtain data directly from their local hospitals; the American Hospital Association Web site also contains links to Metropolitan and Regional Associations and other health care associations.

Analysis Standards

The Council of State and Territorial Epidemiologists (CSTE) has jointly developed a standardized case identification for asthma to identify probable and possible asthma cases in hospital discharge data³.

Confirmed Case: There is no confirmed case classification for hospital discharge data.

Probable Case: Hospital records listing asthma (any ICD-9-CM Code 493; any ICD-10-CM code J45) as the primary discharge diagnosis. (Unlike the ICD codes for mortality, the ICD-10-CM does not include a code for J46 -status asthmaticus).

Possible Case: Hospital records listing asthma (any ICD-9-CM Code 493; any ICD-10-CM Code J45) as a secondary discharge diagnosis OR records for children under 12 years old listing a primary discharge diagnosis of acute bronchitis and bronchiolitis (any ICD-9-CM Code 466) or chronic bronchitis (ICD-9-CM Code 491.20, or 491.21). (Although not specifically stated in the 1998 CSTE statement, acute bronchitis is represented by ICD-10-CM Code J20, acute bronchiolitis is ICD-10-CM Code J21, and chronic bronchitis is represented by ICD-10-CM Code J41-J42.)

Additional ICD-9-CM codes (491, 466, 492, 495, 508, 506.3, 506.9, AND 706) may be used to evaluate for misdiagnosis and for shifts in diagnostic trends that may affect asthma trends.

Asthma hospitalization data are generally presented as rates per 10,000 population.  Standard demographic breakdowns used for analyzing state hospital discharge data are summarized below.

Demographic Breakdowns

• Age Categories: Rates can be calculated by age for single-year, 5-year, 10-year, and infant age intervals.
• Sex Categories: Rates can be calculated separately for “male” and “female” categories.
• Race Categories: Rates can be calculated separately for “White,” “Black” and “Other” categories when data are available.
• Time Trends: Rates can be calculated by year if the cell size permits. Rates also can be calculated by month, day of week, and time of day.
• Geographic Categories: Rates can be calculated at the state, county, city, and zip code levels if the cell sizes permit. Age standardized rates should be used to compare geographic units. It is also important when interpreting these rates to recognize that hospitalization rates for the state may not be independent of county/city rates.

NOTE: Small sample size can result in the release or inferred release of confidential or sensitive information and can also affect reliability of rates. Please consider collapsing years or demographic groups, presenting confidence intervals, or suppressing rates and counts, or a combination of these, if sample size of the numerator or denominator is inadequate. In some cases, an aggregation of categories of data may be necessary to achieve the relative standard error of 30% that has been suggested to produce reliable rates (https://www.cdc.gov/nchs/data/statnt/statnt24.pdfpdf icon). For example, if the event count is <30 in any particular year, we suggest combining years to achieve numerators ≥30, and/or estimating trends based on 3-year rolling averages (e.g., calculate a single rate for 1978 – 1980, then 1979 – 1981, etc.).

National Indicators

Hospital discharge data for asthma are the basis of two sets of national indicators for asthma: the HP2020 objectives⁴ and the National Chronic Disease Indicators for Surveillance⁵. All these indicators use hospitalizations with a primary discharge diagnosis of asthma (ICD-9-CM Code 493) for the numerator and resident population from the U.S. Census for the denominator. These indicators differ slightly in age breakdowns and population of interest:

HP2020 Objective RD–2: Reduce hospitalizations for asthma to:

• 7/10,000 in children and adults age 5 to 64 years (Age-adjusted to the year 2000 standard population) RD-2.2
• 1/10,000 in adults aged 65 years and older (Age adjusted to the year 2000 standard population) RD-2.3^4,7,8.

Chronic Disease Indicators⁵: Several organizations have developed a set of chronic disease indicators for national surveillance purposes. The indicators suggest calculating three measures for both hospitalizations with a primary discharge code of asthma and for hospitalizations with a contributing diagnosis of asthma: 1) the annual number of hospitalizations; 2) the annual rate; and 3) the annual, age-standardized rate (direct standardization to the estimated Year 2000 U.S. population).

Numerator: Select resident hospital discharges during a calendar year with a primary discharge code of asthma or a contributing diagnosis of asthma

Denominator: Total midyear resident population for the same calendar year

Comparison data source: Agency for Healthcare Research and Quality’s (AHRQ) Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases (SID) were used to generate benchmarks for Pediatric Quality Indicators (PDI) based on the analysis of 44 states in 2010. The PDI for Pediatric asthma hospitalizations is to Reduce pediatric asthma hospitalizations in persons under age 18 years to 12.0 per 10,000⁶.

In addition to being used for calculating the asthma hospitalization rates, discharge data can also be used to calculate readmission rates⁹, length of stay, cost of hospitalization, percent of hospitalizations paid for by Medicaid or other sources, and to describe the common comorbidities of asthma hospitalizations. Data can also be linked with other data sources to explore factors related to hospitalization. Thus, these data can be used to identify potential cases of work-related asthma¹⁰. The medical records for these hospitalizations can then be reviewed to confirm the classification.

Limitations of These Data

• Because of multiple hospital admissions for individual persons, these data represent the number of hospitalizations, not the number of persons hospitalized. Without patient identifiers, there is no way to determine how many times a person was hospitalized. However, each hospitalization is an adverse event of major consequences to the person, and thus the count and rate of total hospitalizations is the best reflection of the public health burden experienced by the community.
• Practice patterns and payment mechanisms may affect decisions by health care providers to hospitalize patients.
• A state hospital discharge database may not be a complete census of hospitalizations of their residents. Residents hospitalized in another state may not be reported in his or her state’s hospital data set. Federal hospitals (military and veterans hospitals) are not generally included in state hospital discharge data sets; if a small geographic area includes a military base with a military hospital, then its rates may be artificially low. Furthermore, hospitalizations for out-of-state residents will be included in the data set.  These data need to be included if calculating hospital burden, but it is important to exclude these hospitalizations when calculating a hospitalization rate for state residents.
• Often, data on race (and Hispanic ethnicity) are not reported by some hospitals.

Differences in the Reporting of Asthma Hospitalizations

The National Asthma Control Program (NACP) and other public health programs use hospital discharge dates while the National Environmental Public Health Tracking Network uses the hospital admission dates to count asthma cases. This may cause a difference in asthma rates between the NACP and the Tracking Network websites. For additional information go to http://ephtracking.cdc.gov/showAsthmaCollectingData.action

Federal and State Contacts and Resources for NHDS Data (CDC)

Centers for Disease Control and Prevention Contacts
National Center for Environmental Health
Asthma and Community Health Branch
General Number: (770) 488-3700
Current state asthma contacts:  https://www.cdc.gov/asthma/contacts/default.htm

National Center for Health Statistics
Division of Health Care Statistics
General Number: 1-800-232-4636

References

1. States with Significant Hospital Data Collection Programs, National Association of Health Data Organizations (NAHDO), 2005.  Available at: http://www.hcup-us.ahrq.gov/reports/final_report.pdfpdf iconexternal icon
2. Mendlein JM, Franks D. Hospital discharge data. In:  Using Chronic Disease Data:  A Handbook for Public Health Practitioners. Atlanta:  US Department of Health and Human Services, Public Health Service, 1992.
3. CSTE Environmental and Chronic Disease Committees.  Asthma Surveillance and Case Definition – CSTE Position Statement 1998 – EH/CD 1.  Available at: http://c.ymcdn.com/sites/www.cste.org/resource/resmgr/PS/1998-EHCD-1.pdfpdf iconexternal icon.
4. Healthy People 2020 is available at: http://www.health.gov/healthypeople/external icon
5. Chronic Disease Indicators – Asthma Hospitalizations:  February 2012.  Available at: http://apps.nccd.cdc.gov/cdi/IndDefinition.aspx?IndicatorDefinitionID=92
6. AHRQ Quality Indicators- Pediatric Quality Indicator v4.5 Benchmark Data Tables May 2013. Agency for Healthcare Research and Quality, Rockville, MD.  http://www.qualityindicators.ahrq.gov/Downloads/Modules/PDI/V45/Version_45_Benchmark_Tables_PDI.pdfpdf iconexternal icon
7. Hall MJ, Owings MF. 2000 National Hospital Discharge Data. Advance Data from Vital and Health Statistics. No. 329. Hyattsville, MD:  National Center for Health Statistics (NCHS); June 19, 2002.
8. National Center for Health Statistics. Detailed diagnosis and procedures:  National Hospital Discharge Survey.  NCHS Vital and Health Statistics 13, Published annually.
9. Goldring J, Hanrahan L, Anderson HA, Remington PL. Asthma Hospitalizations and Readmissions Among Children and Young Adults – Wisconsin, 1991 – 1995. Morbidity and Mortality Weekly Report 46(1):726-729 August 8, 1997.
10. Rosenman KD, Reilly JD. Asthma. In: Maizlish NA, ed.  Workplace Health Surveillance:  An Action-Oriented Approach. Oxford University Press, 2000.