Chest
Volume 130, Issue 5, November 2006, Pages 1390-1396
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Original Research
Development of a Contemporary Bleeding Risk Model for Elderly Warfarin Recipients

https://doi.org/10.1378/chest.130.5.1390Get rights and content

Background and purpose

Develop and validate a contemporary bleeding risk model to guide the clinical use of warfarin in the elderly atrial fibrillation (AF) population.

Methods

Chart-abstracted data from the National Registry of Atrial Fibrillation was combined with Medicare part A claims to identify major bleeding events requiring hospitalization. Using a split-sample technique, candidate variables that provided statistically stable relationships with major bleeding events were selected for model development. Three risk categories were created and validated. The new model was compared to existing bleeding risk models using c-statistics and Kaplan-Meier curves.

Results

Model development and validation was conducted on 26,345 AF patients who were > 65 years of age and had been discharged from the hospital while receiving warfarin therapy. The following eight variables were included in the final risk score model: age ≥ 70 years; gender; remote bleeding; recent (ie, during index hospitalization) bleeding; alcohol/drug abuse; diabetes; anemia; and antiplatelet use. Bleeding rates were 0.9%, 2.0%, and 5.4%, respectively, for the groups with low, moderate, and high risk, compared to the bleeding rates for groups with moderate risk (1.5% and 1.0%) and high risk (1.8% and 2.5%) from other models.

Conclusions

Using a nationally derived data set, we developed a model based on contemporary practice standards for determining major bleeding risk among AF patients receiving warfarin therapy. The larger sample size afforded the opportunity to incorporate additional risk factors. In addition, since the majority of our population was > 65 years of age, we had greater ability to stratify risk among the elderly.

Section snippets

Materials and Methods

The study design was a retrospective cohort analysis using the National Registry of Atrial Fibrillation. Briefly, the Centers for Medicare & Medicaid Services authorized the collection of data on a national, random sample of patients discharged from the hospital between April 1998 and March 1999, and between July 2000 and June 2001 with a diagnosis of AF (International Classification of Diseases, ninth revision, clinical modification, code 427.31) as part of the National Stoke Project.4, 5 We

Results

The cohort consisted of 76,177 unique observations. Reasons and counts for exclusion were made in the following order: failure to match with the Medicare denominator file; death before hospital discharge; discharged from the hospital against medical advice or discharged to an acute care hospital (n = 6,666); managed care enrollment (n = 3,215); no warfarin prescribed at the time of hospital discharge (n = 38,089); and age < 65 years (n = 1,862). There were 26,345 study subjects remaining for

Discussion

We were able to identify eight variables that were significant predictors of major bleeding events. The resulting model combining these risk factors performed well in differentiating among low-risk, moderate-risk, and high-risk groups, and likewise performed well when compared with two previous bleeding risk models. Our contemporary model improved the discrimination between subjects at risk for a bleeding event based on areas under the ROC curve and had three categories that demonstrated a

Summary

Using a nationally derived data set, we have developed a model based on contemporary practice standards for determining the risk of major bleeding events among AF patients receiving warfarin therapy. Risk scores can be computed for individuals considering the following eight separately weighted factors: age; gender; recent bleeding event; remote bleeding event; alcohol/drug abuse; diabetes; anemia; and concomitant antiplatelet therapy. Validation of this model in other study populations is

ACKNOWLEDGMENT

The authors acknowledge the assistance of the Iowa Foundation for Medical Care and the Centers for Medicare & Medicaid Services in providing the data that made this research possible.

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    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

    The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

    The conclusions presented are solely those of the authors and do not represent those of the Iowa Foundation for Medical Care or the Centers for Medicare & Medicaid Services.

    The American Heart Association provided funding for this project through grant-in-aid No. 0450071Z.

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