Asthma-related Healthcare Use
Healthcare Cost and Utilization Project (HCUP) — ED visits and hospital inpatient stays with asthma
The Healthcare Cost and Utilization Project (HCUP) is a family of healthcare databases, software tools, supplemental files, reports, and other related products developed through a federal, state, and Industry partnership and sponsored by the Agency for Healthcare Research and Quality (AHRQ). It builds on the data collection efforts of state data organizations, hospital associations, and private data organizations and is the largest collection of all-payer, encounter-level hospital care data in the United States. AHRQ transforms administrative statewide healthcare data into research-ready uniform databases with a common set of data elements. The National (Nationwide) Emergency Department Sample (NEDS) and the National (Nationwide) Inpatient Sample (NIS) databases from the HCUP are used to estimate asthma-related emergency department visits and hospitalizations, respectively.
- The Nationwide Emergency Department Sample (NEDS)
The Nationwide Emergency Department Sample (NEDS) is a large all-payer emergency department (ED) database in the United States, yielding national estimates of hospital-owned ED visits. The NEDS contains unweighted data from over 28 million ED visits each year and weighted estimates of approximately 123 million ED visits. The database tracks information about ED visits across the country, which includes geographic areas, hospital and patient characteristics, and nature of visits (e.g., common reasons for ED visits including acute conditions, chronic conditions, and injuries). For additional information regarding NEDS, go to https://www.hcup-us.ahrq.gov/db/nation/neds/nedsdbdocumentation.jsp.
- The National (Nationwide) Inpatient Sample (NIS)
The National (Nationwide) Inpatient Sample (NIS) is a database focused on inpatient hospital stays. Data in this database are acquired from 48 partners (47 states and the District of Columbia) and represent more than 97 percent of the U.S. population. The NIS includes a sample of all discharges from U.S. community hospitals, excluding rehabilitation and long-term acute care hospitals. The NIS contains unweighted data on more than seven million hospital stays and is ideal for generating national and regional estimates, thus enabling analyses of rare conditions, and special populations. Beginning with the 2012 data, the National Inpatient Sample (NIS) was redesigned to optimize national estimates. Nationwide statistics for years prior to 2012 have been regenerated using new trend weights to permit longitudinal analysis. For additional information regarding NIS, go to https://www.hcup-us.ahrq.gov/db/nation/nis/nisdbdocumentation.jsp.
Web tables for both ED visits and hospital inpatient short stays with asthma as the primary diagnosis include the weighted counts and rates per 10,000 U.S. resident population by selected patient characteristics (e.g., age, sex, race, ethnicity, metropolitan statistical area [MSA] status of patient’s residence location, and U.S. Census regions of hospital location). Data on race and ethnicity are available for hospitalization in NIS database since 1988 (NIS Database Documentation Archive (ahrq.gov)) and it is available for ED visits in NEDS database from 2019 onwards (NEDS Description of Data Elements (ahrq.gov)). Not all HCUP Partner organizations provide information on race and ethnicity, thus the availability of data on race and ethnicity may differ by year and can vary by hospital.
An asthma ED visit was defined as an ED visit with asthma as the primary diagnosis (ICD-9-CM diagnosis code of 493 until the implementation of ICD-10-CM in October 2015 and the diagnosis code of J45). An asthma hospital inpatient stay was defined as a hospital inpatient stay with asthma as the primary diagnosis (ICD-9-CM diagnosis code of 493 until the implementation of ICD-10-CM in October 2015 and diagnosis code of J45). The relative standard error (RSE) of an estimate is used to assess the reliability of the estimates. The RSE of an estimate is calculated by dividing the standard error of the estimate by the estimate itself and is expressed as a percentage of the estimate. If an estimate has a relative standard error of 30 percent or less, the estimate is considered reliable.
Ambulatory Healthcare Data
Physician office visits and emergency department visits data are provided by National Center for Health Statistics (NCHS) annually.
The National Ambulatory Medical Care Survey (NAMCS) is based on a sample of visits to non-federally employed office-based physicians who are primarily engaged in direct patient care and, starting in 2006, a separate sample of visits to community health centers. NAMCS provides objective, reliable information about the provision and use of ambulatory medical care services in the United States. Prior to 2012, NAMCS relied on paper instruments; the survey switched to an automated laptop-assisted data collection method in 2012.
The National Hospital Ambulatory Medical Care Survey (NHAMCS) collects data on the utilization and provision of ambulatory care services in hospital emergency and outpatient departments, and hospital-based ambulatory surgery centers in non-federal, general or short-stay hospitals, exclusive of federal, military, and Veterans Administration hospitals, located in the 50 States and the District of Columbia. The NHAMCS survey of hospital emergency and outpatient departments has been ongoing since 1992. Data on ambulatory surgery performed in hospitals have been collected annually, since 2009. Prior to 2012, NHAMCS relied on paper instruments; the survey switched to an automated laptop-assisted data collection method in 2012.
For additional information regarding the design of the NAMCS/NHAMCS, go to https://www.cdc.gov/nchs/ahcd/index.htm. For the survey description, questionnaires, and related documentation, go to https://www.cdc.gov/nchs/ahcd/ahcd_questionnaires.htm.
NAMCS/NHAMCS web tables for physician office and ED visits with asthma as the primary diagnosis include the weighted count and rate of visits per 10,000 U.S. civilian population by selected patient characteristics. An asthma physician office or ED visit was defined as a visit with asthma as the primary diagnosis (ICD-9-CM diagnosis code of 493 until year 2016 and ICD-10-CM diagnosis code of J45 in 2016 and after). The National Center for Health Statistics considers an estimate to be reliable if it has a relative standard error of 30 percent or less (i.e., the standard error is no more than 30 percent of the estimate).
The sample size of the NHAMCS ED database has continued to decline in recent years, thus limiting the presentation of estimates stratified by select demographic characteristics in the asthma web tables. Therefore, the data source used to estimate asthma ED visit rates for the web tables changed to the HCUP NEDS database starting with 2020 web tables.
NHAMCS asthma ED visits web tables now in the downloadable pdf titled “2010–2019 ED Visits Web Tables—NHAMCS.” This file contains web tables for years 2010 through 2019 for ED visits with asthma as the primary diagnosis that include the weighted counts and rates of visits per 10,000 U.S. civilian non-institutionalized population by selected patient characteristics (e.g., age, sex, race, ethnicity, MSA status, and U.S. Census regions of hospital location).