Healthcare Cost and Utilization Project

HCUP User Support Website (HCUP-US)

The HCUP User Support Website (HCUP-US) is the main repository of information for HCUP. It is designed to answer HCUP-related questions; provide detailed information on HCUP databases, tools, and products; and offer technical assistance to HCUP users. HCUP’s tools, publications, documentation, news, and services; HCUP Fast Stats; and HCUPnet (the free online data query system) all may be accessed through HCUP-US. The Web site also provides information on how to obtain HCUP databases through the HCUP Central Distributor.

HCUP-US is located at http://www.hcup-us.ahrq.gov.

HCUP Overview Course

To help researchers and policymakers discover and use HCUP’s data, tools, and products to their fullest potential, HCUP developed a free, interactive online course that provides an overview of the features, capabilities, and potential uses of HCUP. The course is modular, so users can either move through the entire course or access the resources in which they are most interested. The online HCUP Overview Course can work as both an introduction to HCUP data and tools and a refresher for established users.

HCUP Online Tutorial Series

The HCUP Online Tutorial Series is a set of free interactive courses that provide HCUP data users with information about HCUP data and tools, as well as give trainingon technical methods for conducting research with HCUP data. The online courses are modular, so users can move through an entire course or access the sections in which they are most interested. Available tutorials feature topics such as loading and checking HCUP data, HCUP’s sampling design, calculating standard errors, producing national estimates, conducting multi-year analysis, and using the nationwide readmissions database.

Overview of HCUP Databases

HCUP databases bring together the data collection efforts of State data organizations, hospital associations, private data organizations, and the Federal Government to create an information resource of patient-level health care data.

HCUP includes the largest collection of longitudinal hospital care data in the United States, with all-payer, encounter-level information beginning in 1988. The data are compiled in a uniform format with privacy protections in place. Researchers and policymakers can use HCUP records to identify, track, and analyze national trends in health care use, access, charges, quality, and outcomes. The databases are suited for a broad range of analyses—including rare conditions and special patient populations.

HCUP databases are released approximately 6–18 months after the end of a given calendar year, with State databases available earlier than the national data set. For example, 2016 State data were available beginning in 2017, and 2016 nationwide data were available beginning in July 2018.

Currently there are seven types of HCUP databases: four with national- and regional-level data and three with State- and local-level data.

National Databases—for National and Regional Analyses

• National Inpatient Sample (NIS) (formerly the Nationwide Inpatient Sample): Annual inpatient data from a stratified systematic sample of discharges from all hospitals in HCUP, equal to approximately 20 percent of all discharges in U.S. community hospitals, excluding rehabilitation and long-term acute-care hospitals. Data are available from 1988 forward, and a new database is released annually, approximately 18 months after the end of a calendar year. The NIS Overview and the NIS Database Documentation pages of the HCUP-US Web site contain additional information.
• Kids' Inpatient Database (KID): A nationwide sample of pediatric inpatient discharges designed specifically for users to study a broad range of conditions and procedures related to child health issues. The KID was released every 3 years, from 1997 to 2012 and resumed released again in 2016.
• Nationwide Emergency Department Sample (NEDS): A database of approximately 31 million records that yields national estimates of 143 million emergency department (ED) visits. The NEDS captures encounters in which the patient was admitted for inpatient treatment as well as those in which the patient was treated and released. The NEDS is released annually and is available from 2006 forward.
• Nationwide Readmissions Database (NRD): The NRD is a unique and powerful database designed to support various types of analyses of national readmission rates for all payers and the uninsured. This database addresses a large gap in health care data—the lack of nationally representative information on hospital readmissions for all ages. The NRD is released annually from 2010 forward.

State Databases—for State and Local Analyses

• The State Inpatient Databases (SID): Databases from the universe of inpatient discharge abstracts from participating States, released annually. Data are available from 1995 forward. The SID are released on a rolling basis, as early as 6 months following the end of a calendar year.
• The State Ambulatory Surgery and Services Databases (SASD): Ambulatory surgery encounter abstracts from hospital-affiliated and sometimes freestanding ambulatory surgery sites in participating States. Data are available from 1997 forward. The SASD are released on a rolling basis, as early as 6 months following the end of a calendar year.
• The State Emergency Department Databases (SEDD): Hospital-affiliated ED data for visits in participating States that do not result in hospitalizations. Data are available from 1999 forward. The SEDD are released on a rolling basis, as early as 6 months following the end of a calendar year.

Obtaining HCUP Databases Through the Central Distributor

A number of HCUP State Partners make their data available for purchase through the online HCUP Central Distributor. Applications for the databases are available on its Website. Since March 1, 2016, the national databases have been delivered via secure digital download. Please note, prospective purchasers and all persons with access to the databases are required to take the Data Use Agreement Training Course and sign the Data Use Agreement before using the data.

The price of the data varies by the database and year. Recent years of the NIS are $625 per data year, with a special rate for students of $125. The KID is $500 per data year ($100 for students). The NEDS is $750 per data year ($150 for students). The NRD is $1,000 per data year ($200 for students). The cost of the State databases is set by the individual State Partner supplying the data to HCUP. Pricing varies by State and database, and certain Partners may have different prices for the type of organization requesting the data (nonprofit, government, academic, etc.). Purchasing and pricing information can be found in the Database Catalog on the HCUP-US Web site at http://www.hcup-us.ahrq.gov/tech_assist/centdist.jsp.

HCUPnet

HCUPnet is a free online query system that provides statistics and information from the HCUP national (NIS, KID, NRD, and NEDS) and State (SID, SASD, and SEDD) databases for those States that have agreed to participate.

HCUPnet can be used for identifying, tracking, analyzing, and comparing statistics on hospital inpatient stays, emergency care, and ambulatory surgery as well as for obtaining measures of quality that are based on the AHRQ Quality Indicators ^TM. Select national- and county-level statistics are available. HCUPnet also canbe used for trend analysis with health care data available from 1993 forward.

HCUPnet includes a feature that provides users with some statistics on hospital readmissions within 7 and 30 days of hospital discharge. Information on calculating readmissions for HCUPnet is available in an HCUP Methods Series report.

HCUP Fast Stats

HCUP Fast Stats is a Web-based tool that provides easy access to the latest HCUP-based statistics for health care information topics. HCUP Fast Stats uses visual statistical displays in stand-alone graphs, trend figures, interactive displays, or simple tables to convey complex information at a glance. The first topic in HCUP Fast Stats— State Trends in Hospital Use by Payer (formerly called Effect of Health Insurance Expansion on Hospital Use and Effect of Medicaid Expansion on Hospital Use)—launched in July 2015, with data updates released quarterly starting October 2015. This topic includes statistics from up to 44 States on the number of hospital discharges by payer group (Medicare, Medicaid, private insurance, and uninsured) for categories of conditions (surgical, mental health, injury, maternal, and medical). Users can run State-by-State comparisons and analyze the effects of Medicaid expansion on hospital utilization levels and payment sources.

The second topic—National Hospital Utilization and Costs—was released in December 2015. This topic focuses on national statistics on inpatient stays: Trends, Most Common Diagnoses, and Most Common Operations.

In July 2016, AHRQ updated HCUP Fast Stats to include statistics from ED settings— State Trends in Emergency Department Visits by Payer. These ED statistics are a supplement to the existing State-level inpatient stay trends by expected payer. Quarterly ED visit counts are presented from 2006-2016 for up to 32 States in a given year.

HCUP Fast Stats will continue to be updated regularly (quarterly or annually, as newer data become available) for timely, topic-specific national and State-level statistics.

AHRQ Quality Indicators

The AHRQ Quality Indicators (QIs) are standardized, evidence-based measures of health care quality that make use of readily-available hospital inpatient administrative data. AHRQ QIs can be used to highlight potential quality concerns, identify areas that need further study and investigation, and track clinical performanceand outcomes over time.

The AHRQ QIs consist of four modules measuring various aspects of quality:

• Prevention Quality Indicators can be used with hospital inpatient discharge data to identify quality of care for ambulatory care sensitive conditions. These are conditions for which good outpatient care potentially can prevent the need for hospitalization or for which early intervention can prevent complications or more severe disease.
• Inpatient Quality Indicators reflect quality of care inside hospitals including inpatient mortality for medical conditions and utilization of procedures for which there are questions of overuse, underuse, and misuse.
• Patient Safety Indicators also reflect quality of care inside hospitals but focus on potentially avoidable complications and adverse events following surgeries, procedures, and childbirth.
• Pediatric Quality Indicators reflect quality of care inside hospitals and identify potentially avoidable hospitalizations among children.

Clinical Classifications Software

The Clinical Classifications Software (CCS) provides a method for classifying diagnoses or procedures into clinically meaningful categories. It can be used for aggregate statistical reporting of a variety of topics, such as identifying populations for disease- or procedure-specific studies, or developing statistical reports providing information (i.e., charges and length of stay) about relatively specific conditions.

There are three versions of the CCS Software: Beta CCS for ICD-10-CM/PCS, CCS for ICD-9-CM, and CCS for Services and Procedures.

• Beta CCS for ICD-10-CM/PCS is based on the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM), a uniform and standardized coding system. The Beta CCS for ICD-10-CM/PCS builds on the CCS for ICD-9-CM and attempts to map ICD-10-CM/PCS codes into the same categories.

The multitude of ICD-10-CM/PCS codes—currently more than 69,800 diagnosis codes and 71,900 procedure codes—are collapsed into a smaller number of clinically meaningful categories. The current CCS for ICD-10-CM/PCS version has 285 mutually exclusive categories for diagnoses and 231 for procedures. For certain research interests, this smaller number can be more useful for presenting descriptive statistics than individual ICD-10-CM/PCS codes. Every effort was made to translate the CCS system into ICD-10-CM/PCS without making changes to the CCS assignments for diagnoses and procedures, but because of the new structure and expanded code availability this was not always possible. Because of the increased specificity of ICD-10-CM/PCS and the changes in the two code set structure, it was not possible to translate most multilevel categories to ICD-10-CM/PCS within the current structure – with the exception of the first- and second-level multilevel categories.

The Beta CCS for ICD-10-CM/PCS has been updated annually since October 1, 2015.

• CCS for ICD-9-CM is based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), a uniform and standardized coding system. The CCS for ICD-9-CM provides a method for classifying ICD-9-CM diagnoses or procedures into clinically meaningful categories, which can be used for aggregate statistical reporting of a variety of topics and employed in many types of projects analyzing data on diagnoses and procedures.

Since fiscal year 2008, CCS for ICD-9-CM has included categories from the Clinical Classifications Software for Mental Health and Substance Abuse (CCS-MHSA). These categories replace the original CCS categories for mental health and substance abuse. Specifically, the CCS single-level software includes the CCS-MHSA general categories, and the CCS multi-level software includes the CCS-MHSA-specific categories.

The CCS for ICD-9-CM was updated annually starting January 1980 through September 30, 2015. ICD-9-CM codes were frozen in preparation for ICD-10-CM implementation, and regular maintenance of the codes has been suspended.

• CCS for Services and Procedures provides users with a method of classifying Current Procedural Terminology (CPT®) codes and Healthcare Common Procedure Coding System (HCPCS) codes into 244 clinically meaningful procedure categories. More than 9,000 CPT/HCPCS codes and 6,000 HCPCS codes are accounted for.

The CCS versions and their user guides are available for download from the HCUP-US Website.

Chronic Condition Indicator

The Chronic Condition Indicator (CCI) provides researchers a way to facilitate health services research on diagnoses using administrative data. There are two versions of the CCI software, CCI for ICD-9-CM and Beta CCI for ICD-10-CM. The CCI tools categorize ICD-9-CM/ICD-10-CM diagnoses codes into two classifications: chronic or not chronic. A chronic condition is defined as a condition that lasts 12 months or longer and meets one or both of the following tests: (1) it places limitations on self-care, independent living, and social interactions, and (2) it results in the need for ongoing intervention with medical products, services, and special equipment. The identification of chronic conditions is based on all five-digit ICD-9-CM or seven-digit ICD-10-CM codes. External cause of injury codes are not classified because all injuries are assumed to not be chronic. Currently, there are approximately 14,000 diagnosis codes in version ICD-9-CM and 69,800 diagnosis codes in version ICD-10-CM.

The tool also assigns diagnosis codes into 1 of 18 body system indicator categories, allowing users to create indicators listing which specific body systems are affected by a chronic condition. The body system indicator is based on the chapters of the ICD-9-CM/ICD-10-CM codebooks. This indicator may be useful as a means of counting the number of body systems affected by chronic conditions. Alternatively, the CCS may be used in conjunction with the CCI in order to obtain a count of the number of relatively discrete chronic conditions.

The ICD-9-CM CCI was updated annually and is valid for codes from January 1, 1980 through September 20, 2015. ICD-9-CM codes were frozen in preparation for ICD-10-CM implementation and regular maintenance of the codes has been suspended. The ICD-10-CM CCI is updated annually and is valid for codes from October 1, 2015 forward. The indicators may be downloaded from the online HCUP Central Distributor.

Elixhauser Comorbidity Software

Elixhauser Comorbidity Software assigns variables that identify comorbidities in hospital discharge records using ICD-9-CM or ICD-10-CM diagnosis coding. There are two versions of the Elixhauser Comorbidity Software: the Beta Elixhauser Comorbidity Software for ICD-10-CM and the Elixhauser Comorbidity Software for ICD-9-CM.^[3]

The Beta Elixhauser Comorbidity Software for ICD-10-CM consists of two SAS® computer programs for personal computers. Although the programs are written in SAS, they are distributed in ASCII so that they can be readily adapted to other programming languages. The first program, Creation of Format Library for Elixhauser Comorbidity Groups, generates a SAS format library that maps diagnosis codes into comorbidity indicators. Additional formats are created to exclude conditions that may be complications or that may be related to the principal diagnosis. The second SAS program, Creation of Elixhauser Comorbidity Variables, applies these formats to a data set containing administrative data and then creates the 29 comorbidity variables.^[3]

The Elixhauser Comorbidity Software for ICD-9-CM (Version 3.7) contains a third SAS program, Creation of Elixhauser Comorbidity Index Scores, that applies the weights and creates the two indices for the Elixhauser Comorbidity Software— one for in-hospital mortality and one for readmission. The Elixhauser Comorbidity Software for ICD-9-CM is based on ICD-9-CM and Medicare Severity Diagnosis Related Group (MS-DRG) codes and is valid through September 30, 2015.^[3]

The Elixhauser Software for ICD-9-CM was updated annually from January 1, 1980, through September 30, 2015. The ICD-9-CM codes were frozen in preparation for ICD-10 implementation, and regular maintenance of the codes has been suspended. The Beta Elixhauser Comorbidity Software for ICD-10-CM is updated annually and is based on the ICD-10-CM and MS-DRG codes that are valid through September 30 of the designated fiscal year after October 1, 2015. The Elixhauser Comorbidity Software is available for download on th HCUP-US Website.^[3]

Procedure Classes

Procedure Classes is a tool that facilitates research on hospital services using administrative data by identifying whether an ICD-9-CM or ICD-10-CM procedure is (1) diagnostic or therapeutic and (2) minor or major in terms of invasiveness and/or resource use. There are two versions of the Procedure Classes tool, Procedure Classes for ICD-9-CM and Beta Procedure Classes for ICD-10-CM.

The Procedure Classes provide users an easy way to categorize procedure codes into one of four broad categories: Minor Diagnostic, Minor Therapeutic, Major Diagnostic, and Major Therapeutic.

• Minor Diagnostic: Non-operating room procedures that are diagnostic (e.g., B244ZZZ Ultrasonography of Right Heart)
• Minor Therapeutic: Non-operating room procedures that are therapeutic (e.g., 02HQ33Z, Insertion of Infusion Device Into Right Pulmonary Artery, Percutaneous Approach)
• Major Diagnostic: Procedures that are considered valid operating room procedures by the MS-DRG grouper and that are performed for diagnostic reasons (e.g., 02BV0ZX, Excision of Superior Vena Cava, Open Approach, Diagnostic)
• Major Therapeutic: Procedures that are considered valid operating room procedures by the MS-DRG grouper and that are performed for therapeutic reasons (e.g., 0210093, Bypass Coronoary Artery, One Site from Coronary Artery with Autologous Venous Tissue, Open Approach).

The Procedure Classes for ICD-9-CM tool was updated annually from January 1, 1980, through September 30, 2015. The ICD-9-CM codes were frozen in preparation for ICD-10 implementation, and regular maintenance of the codes has been suspended. The Beta Procedure Classes for ICD-10-PCS tool is updated annually and is valid for codes from October 1, 2015, forward. Procedure Classes tools are available for download from the HCUP-US Web site.

Utilization Flags

Utilization Flags reveal additional information about use of health care services by combining information from Uniform Billy (UB-04) revenue codes and ICD-9-CM or ICD-10-PCS procedure codes to create flags—or indicators—of utilization for a more complete picture of the services rendered in health care settings such as hospitals, emergency departments, and ambulatory surgery centers. There are two versions of the Utilization Flags tool, Utilization Flags for ICD-9-CM and Beta Utilization Flags for ICD-10-CM/PCS

The Utilization Flags can be employed to study a broad range of services, from simple diagnostic tests to resource-intense procedures, such as procedures done in intensive care units. They also can be used to more reliably examine utilization of diagnostic and therapeutic services—beyond the information that can be gleaned from ICD-9-CM or ICD-10-PCS procedure codes alone.

The Utilization Flags for ICD-9-CM were updated annually from January 2003, through September 30, 2015. The ICD-9-CM codes were frozen in preparation for ICD-10 implementation, and regular maintenance o the codes has been suspended. The Beta Utilization Flags for ICD-10-CM/PCS are updated annually and are valid for codes from October 1, 2015, forward. The Utilization Flags are available for download from the HCUP-US Website.

Surgery Flags

Surgery Flag Softwareconsists of a SAS program and two files that include information about the classification of surgical procedures into the borad and narrow definitiions of surgeries in ICD-9-CM or CPT-based inpatient and ambulatory surgery data. There are three versions of the Surgery Flag Software. The initial release in September 2014 is valid for ICD-9-CM codes through September 2013 and CPT codes through December 2013. A second version was released in June 2015. A third version, focusing on CPT only, was released in April 2017. This version brought the Surgery Flag Software up to date for CPT codes through 2017. The software assignments are validated by certified coding specialists.^[4]

The Surgery Flag Software identifies two types of surgical categories are identified: NARROW and BROAD. NARROW surgery is based on a narrow, targeted, and restrictive definition and includes invasive surgical procedures: An invasive therapeutic surgical procedure involving incision, excision, manipulation, or suturing of tissue that penetrates or breaks the skin; typically requires use of an operating room; and requires regional anesthesia, general anesthesia, or sedation to control pain. BROAD surgery includes procedures that fall under the NARROW category as well as less invasive therapeutic surgeries and diagnostic procedures often performed in surgical settings. Users must agree to a license agreement with the American Medical Association to use the Surgery Flags before accessing the software.^[4]

Cost-to-Charge Ratio Files

The Cost-to-Charge Ratio (CCR) Files are hospital-level files designed to convert the hospital total charge data to cost estimates when merged with data elements exclusively in the NIS, KID, NRD, and SID.

The HCUP databases are limited to information on total hospital charges, which reflect the amount billed to the payer per patient encounter. Total charges do not reflect the actual cost of providing care or the payment received by the hospital for services provided. This total charge data can be converted into cost estimates using the CCR Files, which include hospital-wide values of the all-payer inpatient cost-to-charge ratio for nearly every hospital in the participating NIS, KID, NRD, and SID. Cost information was obtained from the hospital accounting reports collected by the Centers for Medicare & Medicaid Services. Researchers and policy makers can use the converted cost estimates to examine a variety of topics, including use and cost of hospital services, health care cost inflation, and how the cost experiences of a given hospital or health plan compare with national or State trends.

The CCR Files are updated annually and are available for the HCUP inaptient databases beginning with 2001 data. The files may be obtained free-of-charge from the online HCUP Central Distributor, ensuring that users receive the proper version of the CCR Files for the year of interest.

Hospital Market Structure Files

The Hospital Market Structure Files (HMS Files) are hospital-level files designed to supplement the data elements in the NIS, KID, and SID databases. The HMS Files contain various measures of hospital market competition. These measures are aggregate and are meant to broadly characterize the intensity of competition that hospitals may be facing under various definitions of market area.

Hospital market definitions were based on hospital locations, and in some cases, patient ZIP Codes. Hospital locations were obtained from the American Hospital Association (AHA) Annual Survey Database, Area Resource File (ARF), HCUP Historical Urban/Rural – County (HURC) file, and ArcView® GIS. Patient ZIP Codes were obtained from the SID.

Users can merge the data elements on the HMS Files to the corresponding NIS, KID, or SID hospitals by the hospital identification number (HOSPID). Using the merged data elements, hospital market structure measures then can be included in analyses.

Hospital market structure measures are generally useful for performing empirical analyses that examine the effects of hospital competition on the cost, access, and quality of hospital services. They are most useful to analysts as a secondary control variable (e.g., for assessing whether a statistical relationship exists between two variables when hospital market structure is controlled).

The HMS Files are updated every three years and available free-of-charge from the online HCUP Central Distributor. The HCUP HMS Files are currently available for 1997, 2000, 2003, 2006, and 2009.

HCUP Supplemental Varibales for Revisit Analyses

The HCUP Supplemental Variables for Revisit Analyses allow users to track sequential visits for a patient within a state and across facilities and hospitals settings (inpatient, ED, and ambulatory surgery) while adhering to strict privacy guidelines. The available clinical information can help users determine whether these sequential visits are unrelated, an expected follow-up, complications from a previous treatment, or an unexpected revisit or rehospitalization. Users must merge the supplemental files with the corresponding SID, SASD, or SEDD for any analysis. Data are available from 2003-2008 in ASCII format. Beginning with 2009 data, the revisit variables are included in the Core file of the HCUP State Databases when possible.

NIS and KID Trend Weights Files

The NIS Trend Weights and KID Trend Weights Files are available to help researchers conduct longitudinal analyses. They are discharge-level files that provide researchers with the trend weights, and data elements in the case of the NIS Trend Weights, that are consistently defined across data years.

American Hospital Association Linkage Files

The American Hospital Association (AHA) Linkage Files are hospital-level files that contain a small number of data elements that allow researchers to supplement the HCUP State databases with information from the AHA Annual Survey Databases (Health Forum, LLC © 2012). The files are designed to support richer empirical analysis in which hospital characteristics may be important factors. Linkage is possible only in States that allow the release of hospital identifiers and is unique by State and year. The HCUP AHA Linkage Files for the SID, SASD, and SEDD are available starting in 2006 form the HCUP-US Web site. These files are provided to users free of charge. However, agreement to the Terms and Conditions is required.

Nationwide Inpatient Sample Hospital Ownership Files

The NIS Hospital Ownership Files are hospital-level files designed to facilitate analysis of the NIS by hospital ownership categories. These HCUP supplemental files allow the user to identify in the 1998-2007 NIS the following three types of hospitals: government, non-Federal; private, nonprofit; and private, invest-own.