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NRD Description of Data Elements
The Nationwide Readmissions Database (NRD) is a set of inpatient databases in the HCUP family designed for readmission analyses. These HCUP databases are created by AHRQ through a Federal-State-Industry partnership.
 
NRD Description of Data Elements

The following links provide data elements descriptions for the Nationwide Readmissions Database (NRD).

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 the NRD. Please note the following:
  • Not all data elements in the NRD are uniformly coded across States.
  • Not all data elements are available each year.
For certain data elements such as, but not limited to, total charges (TOTCHG), more than one percent of NRD 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 (PDF file, 871 KB) provides guidance on alternative approaches to handling missing data.

As a result of the introduction of ICD-10-CM/PCS1 on October 1, 2015 (quarter 4 of 2015 and the start of fiscal year 2016), the United States transitioned from using ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures. Beginning with the quarter 4 of 2015, the names of diagnosis- and procedure-related data elements in the NRD start with the prefix "I10_" to identify the coding scheme. The coding change in 2015 also is signaled by a change in the NRD file structure:
  • The 2015 NRD included nine months of data with ICD-9-CM coding and three months of data with ICD-10-CM/PCS coding because of the mid-year change in diagnosis and procedure coding. The 2015 NRD files had a very different structure than other years and were split into two parts based on the diagnosis and procedure coding system.
  • Beginning with data year 2016, the NRD is an annual, calendar year file with diagnosis and procedure codes reported using only the ICD-10-CM/PCS coding system. Therefore, the file structure is similar to the file structure of the NRD in data years prior to 2015.
Data elements derived from AHRQ software tools which are based on ICD-10-CM/PCS diagnosis and/or procedure codes are not available on the NRD starting in quarter 4 of 2015. For users interested in applying the AHRQ software tools to the ICD-10-CM/PCS-coded data, the AHRQ software tools are available for download on the HCUP Tools & Software section of the HCUP User Support (HCUP-US) website. The Tools Loading tutorial is available to users interested in applying the AHRQ software tools at www.hcup-us.ahrq.gov/tech_assist/tutorials.jsp.

1 ICD-9-CM: International Classification of Diseases, Ninth Revision, Clinical Modification; ICD-10-CM/PCS: International Classification of Diseases, Tenth Revision, Clinical Modification/Procedure Coding System


All NRD data elements are listed in alphabetical order below, showing the NRD file location for years other than 2015 and for 2015. For a description of how HCUP data elements are coded, and uniform values, check the corresponding boxes below and then click the "View Description of Data Elements".
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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.
AGE Age in years at admission 2010-2017 Core Core
APRDRG All Patient Refined DRG 2010-2017 Severity Q1Q3 and Q4 Severity
APRDRG_Risk_Mortality All Patient Refined DRG: Risk of Mortality Subclass 2010-2017 Severity Q1Q3 and Q4 Severity
APRDRG_Severity All Patient Refined DRG: Severity of Illness Subclass 2010-2017 Severity Q1Q3 and Q4 Severity
AWEEKEND Admission day is on a weekend 2010-2017 Core Core
BODYSYSTEMn ICD-9-CM Body system n 2014-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
CHRONBn Chronic Condition Indicators - body system 2010-2013 DX_PR_Grps  
CHRONn ICD-9-CM Chronic Condition Indicators 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
CM_AIDS AHRQ comorbidity measure for ICD-9-CM codes: acquired immune deficiency syndrome 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_ALCOHOL AHRQ comorbidity measure for ICD-9-CM codes: alcohol abuse 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_ANEMDEF AHRQ comorbidity measure for ICD-9-CM codes: deficiency anemias 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_ARTH AHRQ comorbidity measure for ICD-9-CM codes: rheumatoid arthritis/collagen vascular diseases 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_BLDLOSS AHRQ comorbidity measure for ICD-9-CM codes: chronic blood loss anemia 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_CHF AHRQ comorbidity measure for ICD-9-CM codes: congestive heart failure 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_CHRNLUNG AHRQ comorbidity measure for ICD-9-CM codes: chronic pulmonary disease 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_COAG AHRQ comorbidity measure for ICD-9-CM codes: coagulopathy 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_DEPRESS AHRQ comorbidity measure for ICD-9-CM codes: depression 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_DM AHRQ comorbidity measure for ICD-9-CM codes: diabetes, uncomplicated 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_DMCX AHRQ comorbidity measure for ICD-9-CM codes: diabetes with chronic complications 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_DRUG AHRQ comorbidity measure for ICD-9-CM codes: drug abuse 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_HTN_C AHRQ comorbidity measure for ICD-9-CM codes: hypertension (combine uncomplicated and complicated) 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_HYPOTHY AHRQ comorbidity measure for ICD-9-CM codes: hypothyroidism 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_LIVER AHRQ comorbidity measure for ICD-9-CM codes: liver disease 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_LYMPH AHRQ comorbidity measure for ICD-9-CM codes: lymphoma 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_LYTES AHRQ comorbidity measure for ICD-9-CM codes: fluid and electrolyte disorders 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_METS AHRQ comorbidity measure for ICD-9-CM codes: metastatic cancer 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_NEURO AHRQ comorbidity measure for ICD-9-CM codes: other neurological disorders 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_OBESE AHRQ comorbidity measure for ICD-9-CM codes: obesity 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_PARA AHRQ comorbidity measure for ICD-9-CM codes: paralysis 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_PERIVASC AHRQ comorbidity measure for ICD-9-CM codes: peripheral vascular disorders 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_PSYCH AHRQ comorbidity measure for ICD-9-CM codes: psychoses 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_PULMCIRC AHRQ comorbidity measure for ICD-9-CM codes: pulmonary circulation disorders 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_RENLFAIL AHRQ comorbidity measure for ICD-9-CM codes: renal failure 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_TUMOR AHRQ comorbidity measure for ICD-9-CM codes: solid tumor without metastasis 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_ULCER AHRQ comorbidity measure for ICD-9-CM codes: peptic ulcer disease excluding bleeding 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_VALVE AHRQ comorbidity measure for ICD-9-CM codes: valvular disease 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
CM_WGHTLOSS AHRQ comorbidity measure for ICD-9-CM codes: weight loss 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
DIED Died during hospitalization 2010-2017 Core Core
DISCWT Weight to discharges in the universe 2010-2017 Core Core
DISPUNIFORM Disposition of patient, uniform coding 2010-2017 Core Core
DMONTH Discharge month 2010-2017 Core Core
DQTR Discharge quarter 2010-2017 Core Core
DRG DRG in use on discharge date 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
DRG_NoPOA DRG in use on discharge date, calculated without POA 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
DRGVER DRG or MS-DRG grouper version used on discharge date 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
DXCCSn Clinical Classifications Software (CCS): ICD-9-CM diagnosis classification 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
DXMCCSn Multi-Level CCS for ICD-9-CM Diagnoses 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
DXn ICD-9-CM Diagnosis 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
DXVER Diagnosis codes ICD version indicator 2015-2017 Core Q1Q3 and Q4 DX_PR_Grps
E_CCSn Clinical Classifications Software (CCS) for ICD-9-CM External Cause of Injury Code 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
ECODEn ICD-9-CM External Cause of Injury Code 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
E_MCCSn Multi-Level CCS for ICD-9-CM External Cause of Injury Code 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
ELECTIVE Elective versus non-elective admission 2010-2017 Core Core
FEMALE Indicator of sex 2010-2017 Core Core
H_CONTRL Control/ownership of hospital 2010-2017 Hospital Hospital
HCUP_ED HCUP indicator of emergency department record 2010-2017 Core Core
HOSP_BEDSIZE Bedsize of hospital 2010-2017 Hospital Hospital
HOSP_NRD HCUP NRD hospital identification number 2010-2017 Core, Hospital, Severity, Dx_Pr_Grps (Dx_Pr_Grps not available in 2016) Core, Hospital, Q1Q3 and Q4 Severity, Q1Q3 and Q4 Dx_Pr_Grps
HOSP_UR_TEACH Teaching status of hospital 2010-2017 Hospital Hospital
HOSP_URCAT4 Hospital urban-rural designation 2010-2017 Hospital Hospital
I10_DXn ICD-10-CM Diagnosis 2015 Q4 - 2017 Core Q4 DX_PR_Grps
I10_ECAUSEn ICD-10-CM External Cause of Morbidity Code 2015 Q4 - 2016 Core Q4 DX_PR_Grps
I10_NDX Number of ICD-10-CM diagnoses on this discharge 2015 Q4 - 2017 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 - 2017 Core Q4 DX_PR_Grps
I10_PRn ICD-10-PCS Procedure 2015 Q4 - 2017 Core Q4 DX_PR_Grps
KEY_NRD HCUP NRD record identifier 2010-2017 Core, Severity, Dx_Pr_Grps (Dx_Pr_Grps not available in 2016) Core, Q1Q3 and Q4 Severity, Q1Q3 and Q4 Dx_Pr_Grps
LOS Length of stay, cleaned 2010-2017 Core Core
MDC MDC in effect on discharge date 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
MDC_NoPOA MDC in use on discharge date, calculated without POA 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
N_DISC_U Number of discharges in the universe for the stratum 2010-2017 Hospital Hospital
N_HOSP_U Number of hospitals in the universe for the stratum 2010-2017 Hospital Hospital
NCHRONIC ICD-9-CM Number of chronic conditions 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
NDX Number of ICD-9-CM diagnoses on this discharge 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
NECODE Number of ICD-9-CM External of Cause of Injury Codes on this Record 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
NPR Number of ICD-9-CM procedures on this discharge 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
NRD_DaysToEvent Days from "start date" to admission 2010-2017 Core Core
NRD_STRATUM Stratum used to post-stratify hospital 2010-2017 Core, Hospital Core, Hospital
NRD_VisitLink Patient linkage variable in the NRD 2010-2017 Core Core
ORPROC Major operating room ICD-9-CM procedure indicator 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
PAY1 Expected primary payer, uniform 2010-2017 Core Core
PCLASSn ICD-9-CM Procedure class 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
PL_NCHS Patient Location: NCHS Urban-Rural Code 2010-2017 Core Core
PRCCSn Clinical Classifications Software (CCS) for ICD-9-CM Procedures 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
PRDAYn Number of days from admission to procedure n 2014-2017 Core Q1Q3 and Q4 DX_PR_Grps
PRMCCSn Multi-Level CCS for ICD-9-CM Procedures 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
PRn ICD-9-CM Procedure 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
PRVER Procedure codes ICD version indicator 2015-2017 Core Q1Q3 and Q4 DX_PR_Grps
REHABTRANSFER A combined record involving transfer to rehabilitation, evaluation, or other aftercare 2010-2017 Core Core
RESIDENT Identifies patient as a resident of the State in which he or she received hospital care 2010-2017 Core Core
S_DISC_U Number of discharges in the sample for the stratum 2010-2017 Hospital Hospital
S_HOSP_U Number of hospitals in the sample for the stratum 2010-2017 Hospital Hospital
SAMEDAYEVENT Identifies transfer and same-day stay collapsed records 2010-2017 Core Core
SERVICELINE Service line based on ICD-9 codes 2014-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
TOTAL_DISC Number of hospital discharges in the sample 2010-2017 Hospital Hospital
TOTCHG Total charges, cleaned 2010-2017 Core Core
YEAR Calendar year 2010-2017 Core, Hospital Core, Hospital
ZIPINC_QRTL Median household income for patient's ZIP Code (based on current year) 2010-2017 Core Core

Abbreviations: DX, diagnosis; PR, procedure; Q1, discharge quarter 1; Q3, discharge quarter 3; Q4, discharge quarter 4.

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Internet Citation: NRD Description of Data Elements. Healthcare Cost and Utilization Project (HCUP). December 2019. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/nation/nrd/nrddde.jsp.
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Last modified 12/12/19