Related Experiment Video
Updated: Aug 9, 2026
Inverse Probability of Treatment Weighting (Propensity Score) using the Military Health System Data Repository and National Death Index
Published on: January 8, 2020
Assessment of the coding accuracy of warfarin-related bleeding events
Thomas Delate1, Aubrey E Jones1, Nathan P Clark1
1Pharmacy Department, Kaiser Permanente Colorado, 16601 East Centretech Parkway, Aurora, CO 80011, United States.
Insights
International Classification of Diseases, 9th edition (ICD-9) codes can efficiently identify warfarin bleeding events but may over-report. The absence of a code reliably ruled out bleeding, but codes in any position or for major bleeding had high false positive rates.
Area of Science:
- Pharmacovigilance and Drug Safety
- Health Informatics and Data Analytics
- Clinical Epidemiology
Background:
- Administrative datasets using International Classification of Diseases, 9th edition (ICD-9) diagnosis codes offer an efficient method for identifying warfarin-related bleeding events.
- However, the accuracy of these codes in capturing true bleeding events versus non-events requires thorough evaluation, particularly in patients on warfarin therapy.
Purpose of the Study:
- To assess the diagnostic accuracy of bleeding-related ICD-9 codes in identifying true bleeding events among hospitalized patients receiving warfarin.
- To determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of these codes.
Main Methods:
- A cross-sectional study was conducted within an integrated healthcare delivery system.
- Hospitalizations of anticoagulated patients (aged ≥18 years) between January 1, 2014, and March 31, 2014, were identified via administrative data.
- Manual chart review by blinded abstractors was performed to confirm true bleeding events, followed by calculation of performance metrics for ICD-9 codes.
Main Results:
- Of 486 hospitalizations, 57 true bleeding events were identified in anticoagulated patients (mean age 73.4 years, 50% female).
- When ICD-9 codes were in the principal position, performance was: sensitivity 7.0%, specificity 99.8%, PPV 80.0%, NPV 89.0%.
- For codes in any position, performance was: sensitivity 94.7%, specificity 90.9%, PPV 58.1%, NPV 99.2%. For major bleeding, sensitivity was 100%, specificity 83.1%, PPV 14.0%, NPV 100%.
Conclusions:
- The absence of a bleeding ICD-9 code reliably excluded hospitalization for warfarin-related bleeding.
- However, bleeding ICD-9 codes, especially when recorded in any position or for major bleeding, demonstrated high false positive rates.
- Manual chart review is recommended to validate bleeding events identified through administrative data analysis.
Introduction:
Using International Classification of Diseases, 9th edition (ICD-9) diagnosis codes to identify potential warfarin-related bleeding events from administrative datasets is highly efficient but may be prone to identifying non-events. The objective of this study was to evaluate the ability of bleeding-related ICD-9 codes to identify true bleeding events in patients who were receiving warfarin therapy at the time of hospitalization.
Methods:
This was a cross-sectional study conducted in an integrated healthcare delivery system. Anticoagulated patients aged ≥18years and hospitalized between January 1, 2014 and March 31, 2014 were identified using administrative data queries. All hospitalizations were manually chart reviewed by a trained abstractor blinded to hospitalization diagnoses to assess for true bleeding events. Identification of the presence or lack of bleeding-related ICD-9 diagnosis code(s) for each hospitalization was then performed. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each ICD-9 code present.
Results:
There were 486 hospitalizations in 468 anticoagulated patients with 57 true bleeding events identified. Patients had a mean age of 73.4years and 50% were female. For codes in the principal position, sensitivity, specificity, PPV, and NPV were 7.0%, 99.8%, 80.0%, and 89.0%, respectively. For codes in any position, sensitivity, specificity, PPV, and NPV were 94.7%, 90.9%, 58.1%, and 99.2%, respectively. For major bleeding, sensitivity, specificity, PPV, and NPV were 100%, 83.1%, 14.0%, and 100%, respectively.
Conclusions:
While the absence of a bleeding ICD-9 code reliably ruled-out hospitalization for warfarin-related bleeding, bleeding ICD-9 codes in the principal position were rarely used and undesirable false positive rates were identified when ICD-9 codes when recorded in any position and for major bleeding. Manual chart review is recommended to validate bleeding events from administrative data.
Related Concept Videos
01:30Anticoagulant Drugs: Low-Molecular-Weight Heparins
01:29Venous Thrombosis III: Interprofessional Care