Utilizing the HCUP Databases at WMed

The Healthcare Cost and Utilization Project (HCUP) includes the largest current collection of longitudinal care data in the United States. HCUP consists of several nationwide databases available through the Agency for Healthcare Research and Quality (AHRQ). The databases are publicly available (at a fee) and can be used to identify, track, and analyze national trends in healthcare utilization.

WMed has purchased and currently has access to several of the databases, including:

  • National Inpatient Sample (NIS, 1993-2014 & 2016-2023)
  • Kids’ Inpatient Database (KID, 2006, 2009, 2012, 2016, 2019, and 2022)
  • Nationwide Emergency Department Sample (NEDS, 2016-2023)
  • Nationwide Readmissions Database (NRD, 2016-2022)

More information on the HCUP databases can be found on the Healthcare Cost & Utilization Project User Support website.

Access to the data sets available for WMed is overseen by the WMed Data Analytics Services Unit (DASU). Questions on feasibility or availability of data can be sent to dataanalytics@wmed.edu.

All HCUP projects should use the HCUP protocol template. A separate Excel file has also been created to collect International Classification of Diseases (ICD) codes. Directions on how to access the protocol and complete the Excel file are available via PDF or video. Study teams must use this Excel template when submitting ICD codes for a project. It allows for clarity for the biostatisticians building the query and maximizes efficiency. Any questions can be directed to dataanalytics@wmed.edu.

Note: Analysis will not begin for a HCUP project until both documents are finalized and submitted to the Data Analytics Services Unit. Meetings with the biostatisticians will be scheduled as needed.

HCUP Resources

How Do the Databases Differ?

  Population Codes to Use Ideas for Use Does Not Include
National Inpatient Sample (NIS) All Ages

ICD-9-CM
ICD-10-CM

ICD-9-PCS
ICD-10-PCS
  • Can trend incidence
  • Charge/cost data
  • Readmits
  • Medications
  • Labs/Imaging
  • Outpatients
Kids' Inpatient Database (KID) 21 years and younger

ICD-9-CM
ICD-10-CM

ICD-9-PCS
ICD-10-PCS
  • Great for studying congenital conditions
  • Charge/cost data
  • Readmits
  • Medications
  • Lab/Imaging
  • Outpatients
Nationwide Emergency Department Sample (NEDS) All Ages

ICD-9-CM
ICD-10-CM
CPT/HCPCS*

ICD-9/10-PCS
  • *Use CPTs if NOT admitted to same hospital
  • Can exclude admissions
  • Readmits
  • Medications
  • Labs/Imaging (Some may be available)
Nationwide Readmission Database (NRD) All Ages

ICD-9-CM
ICD-10-CM

ICD-9-PCS
ICD-10-PCS
  • Analyze one year at a time
  • Only looks at readmits per calendar year
  • Medications
  • Labs/Imaging
  • Outpatients

FAQs

  • All projects should be submitted through the Project Request and Triage Form. For the question, “Is there a data pull?” select Yes. There will then be an option to select “HCUP”. A project initiation meeting will then be scheduled to discuss research questions and feasibility.

  • A HCUP project timeline varies depending on the study team. Since the HCUP databases include the billable ICD-CM diagnosis and ICD-PCS procedure codes, teams will need to gather the codes of interest they want to include in the study (projects utilizing the NEDS will also need to identify CPT/HCPCS codes). This may involve some extensive research by the study team. If using both ICD9 and ICD10 datasets, diagnosis, and procedures codes will need to be mapped between ICD9 and ICD10 by the study team.

    Once the statistician has received finalized documents (protocol and Excel template with all ICD/PCS/CPT codes included) and a feasibility has been completed, it typically takes 3-4 weeks for the team to receive results. This may vary depending on the complexity of the analyses being completed and the current queue of projects

  • Study teams may submit a Project Request and Triage Form to initiate a project at any time; however, only one project per project lead may be in development at one time. Once a project has been moved to analysis, the Research Navigator will be in contact to discuss meeting for the next project.
  • Due to the data use agreement in place with HCUP, only the biostatisticians and the Director of the Data Analytics Services Unit (DASU) have direct access to the databases. As such, research teams will not have direct access to the database and will only receive aggregate reports related to their research project. Please fill out a Project Request and Triage Form to begin the process.

  • The sheer size of the databases allows for looking at certain rarer diagnoses that may not be prevalent in southwest Michigan. The databases can also be utilized for analyzing incidence (including national estimates), trends (of incidence, mortality, etc.), length of stay, and cost of certain diagnoses. The databases also can be used to examine incidence in specific regions of the U.S.

    If you are not sure which database might be appropriate for your project, you can email dataanalytics@wmed.edu or submit a triage form with research questions you hope to answer. We are happy to discuss the options possible in each database.

  • The different databases cannot be linked. For example, we cannot link hospitalizations between the NIS (Nationwide Inpatient Sample) and the NRD (Nationwide Readmissions Database). A HCUP project can only utilize one of the databases.
    • The sheer size of the databases allows for analysis of rarer diseases and conditions that might not be prevalent in Kalamazoo, MI.
    • It allows for the ability to analyze trends over years.
    • It can be used to make national estimates.
    • It does not require a data pull from outside sources – The databases are queried by the WMed biostatisticians, which can result in quicker data pulls than requesting electronic health record (EHR) data.
    • Some of the variables are limited. For example, there is no lab or medication documentation. The databases only record billable International Classification of Disease (ICD) or Procedure Coding System (PCS) codes (or CPT codes for procedures in NEDS.
    • Some of the databases (NIS, KID, NEDS) do not track readmissions. While NRD can track readmissions, it can only identify readmissions within the same calendar year.
    • There is a significant time commitment up front from study teams to determine which ICD/PCS/CPT codes they are interested in looking at.
    • The HCUP DUA agreement does not allow reporting counts <11 in any field. As such, the WMed biostatisticians will not report any counts (unweighted or weighted) <11.
    • There is not a one-to-one mapping for diagnoses between ICD9 and ICD10; as such, analyzing both can lead to some degree of estimation.

  • Some comorbidities are already included in the HCUP database. They are classified using the Elixhauser Comorbidity software. The table below contains a list of the variables. Note: Some are only available in ICD9 or ICD10 but not both. If teams would rather use these than find individual ICD codes, they can indicate so in the Excel file; simply put “AIDS - Elixhauser”. The diagnosis codes contained within the groups can be found here.

    Note: The comorbidities listed below can be identified using the Elixhauser grouping system; however, we cannot calculate the Elixhauser Comorbidity Indices (Score) as we do not have all the necessary information to do so.

    Diagnosis ICD9 ICD10
    Aids Y Y
    Alcohol Abuse Y Y
    Deficiency Anemias Y Y
    Autoimmune Conditions   Y
    Rheumatoid Arthritis/Collagen Vascular Disease Y  
    Chronic Blood Loss Anemia Y Y
    Lymphoma Y Y
    Leukemia   Y
    Metastatic Cancer Y Y
    Solid Tumor Without Metastasis, In Situ Y Y
    Solid Tumor Without Metastasis, Malignant Y
    Congestive Heart Failure Y Y
    Chronic Pulmonary Disease Y Y
    Coagulopathy Y Y
    Dementia   Y
    Depression Y Y
    Diabetes, Uncomplicated Y Y
    Diabetes With Chronic Complications Y Y
    Drug Abuse Y Y
    Hypertension (Uncomplicated and Complicated) Y Y
    Hypothyroidism Y Y
    Other Thyroid Disorders   Y
    Liver Disease (Mild) Y Y
    Liver Disease (Moderate to Severe) Y
    Fluid and Electrolyte Disorders Y  
    Neurological Disorders Affecting Movement   Y
    Other Neurological Disorders Y Y
    Seizures and Epilepsy   Y
    Obesity Y Y
    Paralysis Y Y
    Peripheral Vascular Disorders Y Y
    Psychoses Y Y
    Pulmonary Circulation Disorders Y Y
    Renal Failure (Moderate) Y Y
    Renal Failure (Severe) Y
    Peptic Ulcer Disease Excluding Bleeding Y Y
    Valvular Disease Y Y
    Weight Loss Y Y
    • ICD CM diagnosis codes can be found here. 
    • ICD PCS procedure codes can be found here. 
    • Note: Only the billable codes (with green arrows) are searchable within the HCUP databases.
    • CPT/HCPCS codes can be found by searching online or by speaking with a professional biller/coder for guidance.
  • The DASU team follows ICMJE authorship guidelines. Since the statistician contributes substantially to the conception or design of the work and the acquisition, analysis, and interpretation of the data, we ask for authorship on a manuscript or presentation.

Recent WMed Publications Using HCUP

A full list can be found in the WMed Library.

  • Nekkanti S, Hickok K, Shrestha M, Edewaard E, Melgar TA. Evaluation of Hospitalizations for Tick-Borne Diseases in the United States from 2002 to 2021. Tropical Medicine and Infectious Disease. 2025; 10(9):238. https://doi.org/10.3390/tropicalmed10090238
  • Mansoor, T., Ismayl, M., Agarwal, S., Gupta, K., Parikh, S., Brubaker, A., … Koshy, S. K. G. (2025). Comparative outcomes of percutaneous coronary intervention in ST-elevation myocardial infarction: an analysis by infarct-related coronary artery. Baylor University Medical Center Proceedings, 38(5), 787–792.  https://doi.org/10.1080/08998280.2025.2530351
  • Taha Mansoor, Ali bin Abdul Jabbar, Siddharth Agarwal, Mahmoud Ismayl, Dmitry Abramov, Sachin Parikh, Austin Brubaker, Arunima Misra, Salim Virani, Vishal Gupta, Abdul Mannan Khan Minhas, Santhosh K.G. Koshy. Racial and ethnic disparities in the prevalence, outcomes, and management of infective endocarditis in the United States. Cardiovascular Revascularization Medicine, (2025), https://doi.org/10.1016/j.carrev.2025.04.014 
  • Mansoor, T, Jabbar, A, Ismayl, M. et al. Cardiogenic Shock With Acute Myocardial Infarction Among Older Adults in the United States. JACC Adv. 2025 Sep, 4 (9). https://doi.org/10.1016/j.jacadv.2025.102078
  • Costa Filho FF, Buckley JD, Furlan A, Campbell S, Hickok K, Kroth PJ. Inpatient complication rates of bronchoscopic lung volume reduction in the United States, CHEST (2024), doi: 10.1016/j.chest.2024.08.012.
  • Lima NA, Cwikla K, Byers-Spencer K, Crumm I, Patel D, Huffman C, McGoff TN, Young J, Melgar TA, Helmstetter N. Malignant cardiac neoplasms and associated malignancies over 16 years in the USA, Journal of Cardiology (2024), doi: 10.1016/j.jjcc.2023.09.004. 
  • Lima NA, Byers-Spencer K, Cwikla K, Huffman C, Diaz M, Melgar TA, Helmstetter N. Benign Cardiac Neoplasms in the United States: A Thirteen-Year Review, Journal of Cardiology (2021), doi: 10.1159/000519290.
  • Lima NA, Patel DA, Sundaram N, De Castro RL, Huffman C, Diaz M, Linares ST, Melgar TA. Hospital admissions for mitral stenosis in pregnancy in the United States: a thirteen-year analysis, American Journal of Cardiovascular Disease (2023).
  • Sieloff EM, Rutledge B, Huffman C, Vos D, Melgar T. National trends and outcomes of genetically inherited non-alcoholic chronic liver disease in the USA: Estimates from the National Inpatient Sample (NIS) database, Gastroenterology Report (2021), doi: 10.1093/gastro/goaa091