NIS Description of Data Elements

The following links provide data elements descriptions for the National (Nationwide) Inpatient Sample (NIS). Record layouts for the NIS files are available under File Specifications.

Data element descriptions explain how the data element is coded in the HCUP databases and what are the uniform values. The descriptions are cumulative across all years of NIS data from 1988 to the current data year. Please note the following:

Not all data elements in the NIS are uniformly coded across States. Please check the "State Specific Notes" section for each data element before analysis.
Not all data elements in the NIS are available from every State.
Not all data elements are available each year.

For certain data elements such as, but not limited to, patient race (RACE) and total charges (TOTCHG), more than one percent of NIS records have missing values. Users are advised to review frequencies for all data elements planned for use in their analysis and to consider analytic methods for dealing with missing data. The HCUP Methods Series Report #2015-01 provides guidance on alternative approaches to handling missing data in the NIS.

NIS File Structure

Other than data year 2015, which was split into two parts because of the switch from ICD-9-CM to ICD-10-CM/PCS coding, the NIS is an annual, calendar year file. There are three discharge-level files and one hospital-level file:

Discharge-level files

Core File is a single file containing commonly used data elements (e.g., age, expected primary payer, ICD-10-CM/PCS codes, total charges).
Severity File is a single file containing additional data elements to aid in identifying the severity of the condition for a specific discharge.
Diagnosis and Procedure Groups File is a single file containing additional information on the ICD-10-CM diagnoses and ICD-10-PCS procedures that is created by the Agency for Healthcare Research and Quality (AHRQ) software tools.
- For data years 2016-2017, this file was not available in the NIS. Data elements derived from the ICD-10-CM/PCS AHRQ software tools were not included in the NIS because they were still in development and testing.
- Beginning with data year 2018, this file is available in the NIS and includes data elements derived from the Clinical Classifications Software Refined (CCSR) for ICD-10-CM diagnoses.
- Beginning with data year 2019, data elements derived from the Elixhauser Comorbidity Software Refined for ICD-10-CM, the CCSR for ICD-10-PCS procedures, and Procedure Classes Refined for ICD-10-CM are also available in this file.

Hospital-level file

Hospital File is a single file containing information on hospital characteristics.

Users interested in applying AHRQ software tools to the NIS for data years including ICD-10-CM/PCS-coded data to produce data elements currently unavailable in the database files may do so by downloading the respective tool(s) from the Research Tools section of the HCUP User Support (HCUP-US) website. Additionally, users may wish to review the HCUP Software Tools Tutorial, which provides instructions on how to apply the AHRQ software tools to HCUP or other administrative databases.

For information on changes to the NIS in data year 2015, refer to the document 2015 Healthcare Cost and Utilization Project (HCUP) National Inpatient Sample: Change in Structure and Data Elements Caused by Transition to ICD-10-CM/PCS.

All NIS data elements are listed in alphabetical order below, showing the NIS file location for years other than 2015 and for 2015. For descriptions of HCUP data elements uniform values, check the corresponding boxes below and then click "View Description of Data Elements".

Check the corresponding boxes and then click View Description of Data Elements (Top of Form)
Abbreviations: DX, diagnosis; PR, procedure; Q1, discharge quarter 1; Q3, discharge quarter 3; Q4, discharge quarter 4.

HCUP Data Element	Descriptive Title	Years	File(s) for years other than 2015	File(s) in 2015
*Select All*	Data elements change frequently, and are only current as of the date generated.
ADAYWK	Admission day of week	1988-1997	Core
AGE	Age in years at admission	1988+	Core	Core
AGE_NEONATE	Neonatal age (first 28 days after birth) indicator	2012+	Core	Core
AGEDAY	Age in days (when AGE is less than 1 year)	1988-2011	Core
AHAID	AHA hospital identifier	1988-2011	Hospital
AMONTH	Admission month	1988+	Core	Core
APRDRG	All Patient Refined DRG	2002+	Severity	Q1Q3 and Q4 Severity
APRDRG_Risk_Mortality	All Patient Refined DRG: Risk of Mortality Subclass	2002+	Severity	Q1Q3 and Q4 Severity
APRDRG_Severity	All Patient Refined DRG: Severity of Illness Subclass	2002+	Severity	Q1Q3 and Q4 Severity
APSDRG	All-Payer Severity-adjusted DRG	2002-2009	Severity
APSDRG_Charge_Weight	All-Payer Severity-adjusted DRG: Charge Weight	2002-2009	Severity
APSDRG_LOS_Weight	All-Payer Severity-adjusted DRG: Length of Stay Weight	2002-2009	Severity
APSDRG_Mortality_Weight	All-Payer Severity-adjusted DRG: Mortality Weight	2002-2009	Severity
ASOURCE	Admission source, uniform coding	1988-2011	Core
ASOURCE_X	Admission source, as received from source	1988-2011	Core
ASOURCEUB92	Admission source, (UB-92 standard coding)	2003-2011	Core
ATYPE	Admission type	1988-2011	Core
AWEEKEND	Admission day is on a weekend	1998+	Core	Core
BODYSYSTEMn	ICD-9-CM Body system n	2014-2015 Q3	Dx_Pr_Grps	Q1Q3 Dx_Pr_Grps (not in Q4)
CCSMGNn	Clinical Classification Software (CCS) for Mental Health and Substance Abuse - General	2005-2006	Dx_Pr_Grps
CCSMSPn	Clinical Classification Software (CCS) for Mental Health and Substance Abuse - Detail	2005-2006	Dx_Pr_Grps
CHRONn	ICD-9-CM Chronic Condition Indicators	2005-2015 Q3	Dx_Pr_Grps	Q1Q3 Dx_Pr_Grps (not in Q4)
CHRONBn	Chronic Condition Indicators - body system	2005-2013	Dx_Pr_Grps
CM_AIDS	AHRQ comorbidity measure for ICD-9-CM codes: acquired immune deficiency syndrome	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_ALCOHOL	AHRQ comorbidity measure for ICD-9-CM codes: alcohol abuse	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_ANEMDEF	AHRQ comorbidity measure for ICD-9-CM codes: deficiency anemias	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_ARTH	AHRQ comorbidity measure for ICD-9-CM codes: rheumatoid arthritis/collagen vascular diseases	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_BLDLOSS	AHRQ comorbidity measure for ICD-9-CM codes: chronic blood loss anemia	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_CHF	AHRQ comorbidity measure for ICD-9-CM codes: congestive heart failure	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_CHRNLUNG	AHRQ comorbidity measure for ICD-9-CM codes: chronic pulmonary disease	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_COAG	AHRQ comorbidity measure for ICD-9-CM codes: coagulopathy	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_DEPRESS	AHRQ comorbidity measure for ICD-9-CM codes: depression	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_DM	AHRQ comorbidity measure for ICD-9-CM codes: diabetes, uncomplicated	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_DMCX	AHRQ comorbidity measure for ICD-9-CM codes: diabetes with chronic complications	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_DRUG	AHRQ comorbidity measure for ICD-9-CM codes: drug abuse	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_HTN_C	AHRQ comorbidity measure for ICD-9-CM codes: hypertension (combine uncomplicated and complicated)	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_HYPOTHY	AHRQ comorbidity measure for ICD-9-CM codes: hypothyroidism	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_LIVER	AHRQ comorbidity measure for ICD-9-CM codes: liver disease	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_LYMPH	AHRQ comorbidity measure for ICD-9-CM codes: lymphoma	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_LYTES	AHRQ comorbidity measure for ICD-9-CM codes: fluid and electrolyte disorders	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_METS	AHRQ comorbidity measure for ICD-9-CM codes: metastatic cancer	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_NEURO	AHRQ comorbidity measure for ICD-9-CM codes: other neurological disorders	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_OBESE	AHRQ comorbidity measure for ICD-9-CM codes: obesity	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_PARA	AHRQ comorbidity measure for ICD-9-CM codes: paralysis	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_PERIVASC	AHRQ comorbidity measure for ICD-9-CM codes: peripheral vascular disorders	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_PSYCH	AHRQ comorbidity measure for ICD-9-CM codes: psychoses	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_PULMCIRC	AHRQ comorbidity measure for ICD-9-CM codes: pulmonary circulation disorders	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_RENLFAIL	AHRQ comorbidity measure for ICD-9-CM codes: renal failure	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_TUMOR	AHRQ comorbidity measure for ICD-9-CM codes: solid tumor without metastasis	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_ULCER	AHRQ comorbidity measure for ICD-9-CM codes: peptic ulcer disease excluding bleeding	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_VALVE	AHRQ comorbidity measure for ICD-9-CM codes: valvular disease	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CM_WGHTLOSS	AHRQ comorbidity measure for ICD-9-CM codes: weight loss	2002-2015 Q3	Severity	Q1Q3 Severity (not in Q4)
CMR_aaa	Elixhauser Comorbidity Measure Refined for ICD-10-CM diagnosis codes	2019+	DX_PR_GRPS
CMR_VERSION	Version of the Elixhauser Comorbidity Measure Refined for ICD-10-CM diagnosis codes	2019+	DX_PR_GRPS
D10CWT_U	10% sample weight to discharges in the universe	1988-1997	Hospital
DCCHPRn	Clinical Classifications Software: diagnosis classification	1988-1997	Core
DIED	Died during hospitalization	1988+	Core	Core
DISCWT	Weight to discharges in the universe	1998+	Core, Hospital	Core, Hospital
DISCWT_F	Weight to discharges in frame states	1988-1997	Hospital
DISCWT_S	Weight to discharges in state	1988-1997	Hospital
DISCWT_U	Weight to discharges in universe	1988-1997	Hospital
DISCWT10	10% sample weight to discharges in the universe	1998-2004	Subsample
DISCWTcharge	Weight to discharges in the universe for national estimates of total charge in 2000.	2000	Core, Hospital
DISCWTcharge10	10% sample weight to discharges in the universe for national estimates of total charge in 2000.	2000	Subsample
DISP	Disposition of patient	1988-1997	Core
DISPUB04	Disposition of patient, UB04 standard coding	2007-2011	Core
DISPUB92	Disposition of patient, UB92 coding	1998-2006	Core
DISPUNIFORM	Disposition of patient, uniform coding	1998+	Core	Core
DQTR	Discharge quarter	1988+	Core	Core
DQTR_X	Discharge quarter, as received from data source	2006-2011	Core
DRG	DRG in use on discharge date	1988+	Core	Q1Q3 and Q4 Dx_Pr_Grps
DRG_NoPOA	DRG in use on discharge date, calculated without POA	2008+	Core	Q1Q3 and Q4 Dx_Pr_Grps
DRG10	DRG, Version 10	1988-1999	Core
DRG18	DRG, Version 18	1998-2005	Core
DRG24	DRG, Version 24	2006-2014	Core
DRGVER	DRG or MS-DRG grouper version used on discharge date	1988+	Core	Q1Q3 and Q4 Dx_Pr_Grps
DS_DX_Category1	Disease Staging: Principal Disease Category	2002-2010	Severity
DS_LOS_Level	Disease Staging: Length of Stay Level	2002-2007	Severity
DS_LOS_Scale	Disease Staging: Length of Stay Scale	2002-2007	Severity
DS_Mrt_Level	Disease Staging:Mortality Level	2002-2007	Severity
DS_Mrt_Scale	Disease Staging: Mortality Scale	2002-2007	Severity
DS_RD_Level	Disease Staging: Resource Demand Level	2002-2007	Severity
DS_RD_Scale	Disease Staging: Resource Demand Scale	2002-2007	Severity
DS_Stage1	Disease Staging: Stage of Principal Disease Category	2002-2010	Severity
DSHOSPID	Data source hospital number	1988-2011	Core
DSNDX	Maximum number of diagnoses provided by source	1988-1997	Core
DSNPR	Maximum number of procedures provided by source	1988-1997	Core
DSNUM	Date source identification number	1988-1997	Core
DSTYPE	Data source type	1988-1997	Core
DXn	ICD-9-CM Diagnosis	1988-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
DXCCSn	Clinical Classifications Software (CCS): ICD-9-CM diagnosis classification	1998-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
DXCCSR_Default_DX1	Default Clinical Classifications Software Refined (CCSR) for principal/first-listed ICD-10-CM diagnosis	2018+	DX_PR_GRPS
DXCCSR_VERSION	Version of the Clinical Classifications Software Refined (CCSR) for ICD-10-CM diagnosis codes	2018+	DX_PR_GRPS
DXCCSR_AAAnnn	Clinical Classifications Software Refined (CCSR): ICD-10-CM Diagnosis Classification within Body System AAA	2018+	DX_PR_GRPS
DXMCCSn	Multi-Level CCS for ICD-9-CM Diagnoses	2009-2015 Q3	Dx_Pr_Grps	Q1Q3 Dx_Pr_Grps (not in Q4)
DXSYS	Diagnosis coding system	1988-1997	Core
DXVER	Diagnosis codes ICD version indicator	2015-2017	Core	Q1Q3 and Q4 Dx_Pr_Grps
DXVn	Diagnosis validity flag: Diagnosis n	1988-1997	Core
E_CCSn	Clinical Classifications Software (CCS) for ICD-9-CM External Cause of Injury Code	2003-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
E_MCCSn	Multi-Level CCS for ICD-9-CM External Cause of Injury Code	2009-2015 Q3	Dx_Pr_Grps	Q1Q3 Dx_Pr_Grps (not in Q4)
ECCSMGNn	Clinical Classification Software (CCS) for Mental Health and Substance Abuse - General	2005-2006	Dx_Pr_Grps
ECODEn	ICD-9-CM External Cause of Injury Code	2003-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
ELECTIVE	Elective versus non-elective admission	2002+	Core	Core
FEMALE	Indicator of sex	1998+	Core	Core
H_BEDSZ	Bedsize of hospital (definition used prior to 1998)	1993-1997	Hospital
H_CONTRL	Control/ownership of hospital	1993-1997, 2008+	Hospital	Hospital
H_LOC	Location of hospital (definition used prior to 1998)	1993-1997	Hospital
H_LOCTCH	Location/teaching status of hospital (definition used prior to 1998)	1993-1997	Hospital
H_REGION	Hospital census region	1993-1997	Hospital
H_TCH	Hospital teaching status (definition used prior to 1998)	1993-1997	Hospital
HCUP_ED	HCUP indicator of emergency department record	2007+	Core	Core
HFIPSSTCO	Hospital FIPS State/County code	2004-2011	Hospital
HOSP_BEDSIZE	Bedsize of hospital	1998+	Hospital	Hospital
HOSP_CONTROL	Control/ownership of hospital	1998-2011	Hospital
HOSP_DIVISION	Census Division of hospital (STRATA)	2012+	Core, Hospital	Core, Hospital
HOSP_LOCATION	Location (urban/rural) of hospital	1998-2011	Hospital
HOSP_LOCTEACH	Location/teaching status of hospital	1998+	Hospital	Hospital
HOSP_LPNFTEAPD	LPN FTEs per 1000 adjusted inpatient days	2007-2011	Hospital
HOSP_MHSCLUSTER	Multi-hospital system cluster code	2007-2011	Hospital
HOSP_MHSMEMBER	Multi-hospital system membership	2007-2011	Hospital
HOSP_NAFTEAPD	Nurse aides per 1000 adjusted inpatient days	2007-2011	Hospital
HOSP_NIS	NIS hospital number	2012+	Core, Hospital, Severity, Dx_Pr_Grps(Dx_Pr_Grps file not available after 2016)	Core, Hospital, Q1Q3 and Q4 Severity, Q1Q3 and Q4 Dx_Pr_Grps
HOSP_OPSURGPCT	Percentage of all surgeries performed in the outpatient setting	2007-2011	Hospital
HOSP_REGION	Region of hospital	1998+	Hospital	Hospital
HOSP_RNFTEAPD	RN FTEs per 1000 adjusted inpatient days	2007-2011	Hospital
HOSP_RNPCT	Percentage of RNs among all nurses (RNs and LPNs)	2007-2011	Hospital
HOSP_TEACH	Teaching status of hospital	1998-2011	Hospital
HOSPADDR	Hospital address from AHA Annual Survey	1993-2011	Hospital
HOSPBRTH	ICD-9-CM diagnosis indicates in-hospital birth	2006-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
HOSPCITY	Hospital city from AHA Annual Survey	1993-2011	Hospital
HOSPID	HCUP hospital identification number	1998-2011	Core, Hospital, Severity, Dx_Pr_Grps
HOSPNAME	Hospital name from AHA Annual Survey	1993-2011	Hospital
HOSPST	Hospital State postal code	1988-2011	Core, Hospital
HOSPSTCO	Hospital modified FIPS state/county code	1988-2011	Core (1988-2002), Hospital (2002-2011)
HOSPWT	Weight to hospitals in the universe	1998-2011	Hospital
HOSPWT_F	Weight to hospitals in the frame states	1988-1997	Hospital
HOSPWT_S	Weight to hospitals in the state	1988-1997	Hospital
HOSPWT_U	Weight to hospitals in the universe	1988-1997	Hospital
HOSPZIP	Hospital zip code from AHA Annual Survey	1993-2011	Hospital
I10_BIRTH	ICD-10-CM Birth Indicator	2019+	Core
I10_DELIVERY	ICD-10-CM Delivery Indicator	2019+	Core
I10_DXn	ICD-10-CM Diagnosis	2015 Q4, 2016+	Core	Q4 Dx_Pr_Grps
I10_ECAUSEn*	ICD-10-CM External Cause of Morbidity Code	2015 Q4, 2016	Core	Q4 Dx_Pr_Grps
I10_INJURY	Injury ICD-10-CM diagnosis reported on record	2019+	Core
I10_MULTINJURY	Multiple ICD-10-CM injuries reported on record	2019+	Core
I10_NDX	Number of ICD-10-CM diagnoses on this discharge	2015 Q4, 2016+	Core	Q4 Dx_Pr_Grps
I10_NECAUSE*	Number of ICD-10-CM External Cause of Morbidity codes on this record	2015 Q4, 2016	Core	Q4 Dx_Pr_Grps
I10_NPR	Number of ICD-10-PCS procedures on this discharge	2015 Q4, 2016+	Core	Q4 Dx_Pr_Grps
I10_PRn	ICD-10-PCS Procedure	2015 Q4, 2016+	Core	Q4 Dx_Pr_Grps
I10_SERVICELINE	Service line based on ICD-10-CM/PCS codes	2019+	Core
IDNUMBER	Modified AHA hospital identifier	1988-2011	Hospital
KEY	Unique record identifier	1998-2011	Core, Severity, Dx_Pr_Grps
KEY_NIS	NIS record number	2012+	Core, Severity, Dx_Pr_Grps (Dx_Pr_Grps not available after 2016)	Core, Q1Q3 and Q4 Severity, Q1Q3 and Q4 Dx_Pr_Grps
LOCTEACH	Hospital location and teaching status	1988-1992	Hospital
LOS	Length of stay, cleaned	1988+	Core	Core
LOS_X	Length of stay, as received from data source	1988-2011	Core
MDC	MDC in effect on discharge date	1988+	Core	Q1Q3 and Q4 Dx_Pr_Grps
MDC_NoPOA	MDC in use on discharge date, calculated without POA	2009+	Core	Q1Q3 and Q4 Dx_Pr_Grps
MDC10	MDC, Version 10	1988-1999	Core
MDC18	MDC, Version 18	1998-2005	Core
MDC24	MDC, Version 24	2006-2014	Core
MDID_S	Synthetic attending physician number	1988-2000	Core
MDNUM1_R	Physician 1 number (re-identified)	2003-2009	Core
MDNUM1_S	Physician 1 number (synthetic)	2001-2002	Core
MDNUM2_R	Physician 2 number (re-identified)	2003-2009	Core
MDNUM2_S	Physician 2 number (synthetic)	2001-2002	Core
N_DISC_F	Number of frame state discharges in STRATUM	1988-1997	Hospital
N_DISC_S	Number of state's discharges in STRAT_ST	1988-1997	Hospital
N_DISC_U	Number of universe discharges in the stratum	1988+	Hospital	Hospital
N_HOSP_F	Number of frame state hospitals in STRATUM	1988-1997	Hospital
N_HOSP_S	Number of state's hospitals in STRAT_ST	1988-1997	Hospital
N_HOSP_U	Number of universe hospitals in the stratum	1988+	Hospital	Hospital
NCHRONIC	ICD-9-CM Number of chronic conditions	2008-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
NDX	Number of ICD-9-CM diagnoses on this discharge	1988-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
NECODE	Number of ICD-9-CM External of Cause of Injury Codes on this Record	2003-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
NEOMAT	Neonatal and/or maternal ICD-9-CM DX and/or PR	1988-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
NIS_STRATUM	Stratum used to post-stratify hospital	1998+	Core (2000+), Hospital	Core, Hospital
NPR	Number of ICD-9-CM procedures on this discharge	1988-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
ORPROC	Major operating room ICD-9-CM procedure indicator	2008-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
PAY1	Expected primary payer, uniform	1988+	Core	Core
PAY1_N	Expected primary payer, nonuniform	1988-1997	Core
PAY1_X	Expected primary payer, as received from data source	1998-2011	Core
PAY2	Expected secondary payer, uniform	1988-2011	Core
PAY2_N	Expected secondary payer, nonuniform	1988-1997	Core
PAY2_X	Expected secondary payer, as received from data source	1998-2011	Core
PCCHPRn	Physician 1 number (synthetic)	1988-1997	Core
PCLASSn	Procedure Classes Refined for ICD-10-PCS procedure codes	2005-2015 Q3; 2019+	Dx_Pr_Grps	Q1Q3 Dx_Pr_Grps (not in Q4)
PCLASS_ORPROC	Major operating room ICD-10-PCS procedure indicator	2019+	Core
PCLASS_VERSION	Version of the Procedure Classes Refined for ICD-10-PCS procedure codes	2019+	DX_PR_GRPS
PL_NCHS	Patient Location: NCHS Urban-Rural Code	2013+	Core	Core
PL_NCHS2006	Patient Location: NCHS Urban-Rural Code, 2006	2007-2012	Core
PL_UR_CAT4	Patient Location: Urban-Rural 4 Categories	2003-2006	Core
PointOfOriginUB04	Point of origin for admission or visit, UB04 standard coding	2007-2011	Core
PointOfOrigin_X	Point of origin for admission or visit, as received from source	2007-2011	Core
PRn	ICD-9-CM Procedure	1988-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
PRCCSn	Clinical Classifications Software (CCS) for ICD-9-CM Procedures	1998-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
PRCCSR_aaannn	Clinical Classifications Software Refined (CCSR): ICD-10-PCS Procedure Classification within Clinical Domain aaa	2019+	DX_PR_GRPS	Q1Q3 Dx_Pr_Grps (not in Q4)
PRCCSR_VERSION	Version of the Clinical Classifications Software Refined (CCSR) for ICD-10-PCS procedure codes	2019+	DX_PR_GRPS
PRDAYn	Number of days from admission to procedure n	1988+	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
PRMCCSn	Multi-Level CCS for ICD-9-CM Procedures	2009-2015 Q3	Dx_Pr_Grps	Q1Q3 Dx_Pr_Grps (not in Q4)
PROCESS	HCUP processing identification record number	1988-1997	Core
PRSYS	Procedure coding system	1988-1997	Core
PRVER	Procedure codes ICD version indicator	2015-2017	Core	Q1Q3 and Q4 Dx_Pr_Grps
PRVn	Validity Flag: Procedure n	1988-1997	Core
RACE	Race/ethnicity of patient	1988+	Core	Core
S_DISC_S	Number of sample discharges in STRAT_ST	1988-1997	Hospital
S_DISC_U	Number of discharges in the sample for the stratum	1988+	Hospital	Hospital
S_HOSP_S	Number of sample hospitals in STRAT_ST	1988-1997	Hospital
S_HOSP_U	Number of hospitals in the sample for the stratum	1988+	Hospital	Hospital
SEQ	Sequence number	1988-1997	Core
SEQ_SID	HCUP SID sequence number	1993-1997	Core
SERVICELINE	Service line based on ICD-9 codes	2014-2015 Q3	Core	Q1Q3 Dx_Pr_Grps (not in Q4)
SEX	Sex of the patient	1988-1997	Core
ST_BEDSZ	Bedsize category	1988-1992	Hospital
ST_OWNER	Ownership/control category	1988-1992	Hospital
ST_REG	Hospital census region	1988-1992	Hospital
STRAT_ST	Stratum for state-specific weights	1988-1997	Hospital
STRATUM	Stratum used to post-stratify hospital	1988-1997	Hospital
SURGID_S	Synthetic primary surgeon number	1988-2000	Core
TOTAL_DISC	Number of hospital discharges in the sample	1998+	Hospital	Hospital
TOTCHG	Total charges, cleaned	1988+	Core	Core
TOTCHG_X	Total charges, as received from data source	1988-2011	Core
TOTDSCHG	Total hospital discharges	1988-1997	Hospital
TRAN_IN	Indicator of a transfer into the hospital	2008+	Core	Core
TRAN_OUT	Transfer out indicator	2010+	Core	Core
YEAR	Calendar year	1988+	Core, Hospital	Core, Hospital
ZIPINC	Median household income for patient's ZIP Code (based on 1999 demographics)	1998-2002	Core
ZIPINC_QRTL	Median household income for patient's ZIP Code (based on current year)	2003+	Core	Core
ZIPINC4	Median income for patient's ZIP Code (4 categories)	1988-1997	Core
ZIPINC8	Median income for patient's ZIP Code (8 categories)	1988-1997	Core
Abbreviations: DX, diagnosis; PR, procedure; Q1, discharge quarter 1; Q3, discharge quarter 3; Q4, discharge quarter 4. *Beginning with 2017, external cause codes are at the end of the ICD-10-CM diagnosis array.

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