Using highly variable warfarin dosing to identify patients at risk for adverse events

Thrombosis Journal

Adam J Rose¹  Lori E Henault²  Al Ozonoff³  Mary Evans²  Lyndonna Marrast² 

[1] Center for Health Quality, Outcomes, and Economic Research, Bedford VA Medical Center, Bedford, MA, USA;Department of Medicine, Boston University School of Medicine, Boston Medical Center, Boston, MA, USA;Biostatistics Section, Children's Hospital of Boston, Boston, MA, USA

关键词: warfarin.;    risk factors;    medication therapy management;    dose variability;    anticoagulants;   

Others  :  839020
DOI  :  10.1186/1477-9560-9-14

 received in 2011-05-12, accepted in 2011-10-10,  发布年份 2011

【 摘 要 】

Background

Patients who receive highly variable doses of warfarin may be at risk for poor anticoagulation control and adverse events. However, we lack a system to identify patients with the highest dose variability. Our objectives were to develop a scoring system to identify patients with high dose variability, and to validate this new measure by demonstrating that patients so identified have poor anticoagulation control and higher rates of adverse events (criterion validity).

Methods

We used a database of over 4, 000 patients who received oral anticoagulation in community practice between 2000-2002. We reviewed the charts of 168 patients with large warfarin dose variation and agreed on 18 risk factor definitions for high dose variability. We identified 109 patients with the highest dose variability (cases), as measured by coefficient of variation (CoV, SD/mean). We matched each case to two controls with low dose variability. Then, we examined all 327 charts, blinded to case/control status, to identify the presence or absence of the 18 risk factors for dose variability. We performed a multivariable analysis to identify independent predictors of high CoV. We also compared anticoagulation control, as measured by percent time in therapeutic range (TTR), and rates of adverse events between groups.

Results

CoV corresponded with other measures of anticoagulation control. TTR was 53% among cases and 79% among controls (p < 0.001). CoV also predicted adverse events. Six cases experienced a major hemorrhage versus 1 control (p < 0.001) and 3 cases had a thromboembolic event versus 0 control patients (p = 0.04). Independent predictors of high dose variability included hospitalization (OR = 21.3), decreased oral intake (OR = 12.2), use of systemic steroids (OR = 6.1), acetaminophen (OR = 4.0) and antibiotics (OR = 2.7; p < 0.05 for all).

Conclusion

CoV can be used to identify patients at risk for poor anticoagulation control and adverse events. This new measure has the potential to identify patients at high risk before they suffer adverse events.

【 授权许可】

   
2011 Marrast et al; licensee BioMed Central Ltd.

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