Related Experiment Video
Updated: Feb 18, 2026
Inverse Probability of Treatment Weighting Propensity Score using the Military Health System Data Repository and National Death Index
Published on: January 8, 2020
Validity of Using Inpatient and Outpatient Administrative Codes to Identify Acute Venous Thromboembolism: The CVRN
Margaret C Fang1, Dongjie Fan, Sue Hee Sung
1*Division of Hospital Medicine, University of California, San Francisco †Division of Research, Kaiser Permanente Northern California, Oakland, CA ‡Department of Pharmacotherapy, University of Utah College of Pharmacy, Salt Lake City, UT §Office for Health Services, Marshfield Clinic Research Foundation, Marshfield, WI ∥Geisinger Health System, Center for Health Research, Danville, PA ¶Scripps Translational Science Institute, La Jolla, CA #Departments of Epidemiology, Biostatistics and Medicine, University of California, San Francisco **Department of Health Research and Policy, Stanford University School of Medicine, Palo Alto, CA.
Insights
Administrative data using International Classification of Diseases, Ninth Revision (ICD-9) codes are unreliable for identifying venous thromboembolism (VTE) in outpatients. New methods are needed to accurately identify VTE in this population for research and quality reporting.
Area of Science:
- Health Services Research
- Medical Informatics
- Epidemiology
Background:
- Administrative data, including International Classification of Diseases, Ninth Revision (ICD-9) codes, are commonly used for identifying venous thromboembolism (VTE).
- The accuracy of these VTE codes, particularly in outpatient settings, has not been thoroughly validated.
- Reliable identification of VTE is crucial for research and quality reporting initiatives.
Purpose of the Study:
- To evaluate the predictive accuracy of ICD-9 codes for identifying chart-confirmed acute VTE.
- To compare the validity of VTE codes between inpatient and outpatient settings.
- To assess the impact of code position (primary vs. secondary) and VTE type on code accuracy.
Main Methods:
- A cohort of 4642 adults with incident ICD-9 VTE diagnoses (2004-2010) was analyzed.
- Medical charts were reviewed to confirm acute VTE events.
- Positive predictive values (PPVs) were calculated, stratified by VTE type (PE, DVT), code position, and setting (hospital/ED vs. outpatient).
Main Results:
- The PPV for any VTE diagnosis was significantly lower in outpatients (30.9%) compared to hospital/ED patients (64.6%).
- Primary diagnosis codes in hospital/ED settings were more accurate (78.9%) than secondary codes (44.4%).
- Outpatient VTE codes demonstrated poor predictive value for acute VTE (28.0% for PE, 53.6% for lower extremity DVT).
Conclusions:
- ICD-9 codes from outpatient encounters or secondary diagnoses are not reliable for identifying acute VTE.
- Current coding practices necessitate the development of more accurate methods for VTE identification in outpatients.
- Improved VTE identification strategies are essential before administrative codes can be confidently used for research and policy in outpatient settings.
Background:
Administrative data are frequently used to identify venous thromboembolism (VTE) for research and quality reporting. However, the validity of these codes, particularly in outpatients, has not been well-established.
Objective:
To determine how well International Classification of Diseases, Ninth Revision (ICD-9) codes for VTE predict chart-confirmed acute VTE in inpatient and outpatients.
Patients And Methods:
We selected 4642 adults with an incident ICD-9 diagnosis of VTE between years 2004 and 2010 from the Cardiovascular Research Network Venous Thromboembolism cohort study. Medical charts were reviewed to determine validity of events. Positive predictive values (PPVs) of ICD-9 codes were calculated as the number of chart-validated VTE events divided by the number with specific VTE codes. Analyses were stratified by VTE type [pulmonary embolism (PE), deep venous thrombosis (DVT)], code position (primary, secondary), and setting [hospital/emergency department (ED), outpatient].
Results:
The PPV for any diagnosis of VTE was 64.6% for hospital/ED patients and 30.9% for outpatients. Primary diagnosis codes from hospital/ED patients were more likely to represent acute VTE than secondary diagnosis codes (78.9% vs. 44.4%, P<0.001). Primary hospital/ED codes for PE and lower extremity DVT had higher PPV than for upper extremity DVT (89.1%, 74.9%, and 58.1%, respectively). Outpatient codes were poorly predictive of acute VTE: 28.0% for PE and 53.6% for lower extremity DVT.
Conclusions:
ICD-9 codes for VTE obtained from outpatient encounters or from secondary diagnosis codes do not reliably reflect acute VTE. More accurate ways of identifying VTE in outpatients are needed before these codes can be adopted for research or policy purposes.
Related Concept Videos
01:29Venous Thrombosis III: Interprofessional Care
01:20Venous Thrombosis II: Clinical Manifestations and Diagnostic Studies
01:30Venous Thrombosis IV: Nursing Management
01:29Pulmonary Embolism II: Diagnostic Studies and Interprofessional Care
01:26Varicose Veins II: Diagnostic Studies and Interprofessional Care
01:27Pulmonary Embolism III: Nursing Management