Assessing the Risk of Bleeding in Patients With Atrial Fibrillation: the Loire Valley Atrial Fibrillation Project
What is the relative effectiveness of the HAS-BLED bleeding risk score versus other, older bleeding risk scores, and the new ATRIA risk score, in predicting bleeding in anticoagulated patients with atrial fibrillation?
The authors reported the results of a registry of patients diagnosed with atrial fibrillation or atrial flutter at the Department of Cardiology at the Centre Hospitalier Régional et Universitaire in Tours (France), between 2000 and 2010, which included four hospitals in an area serving approximately 400,000 inhabitants. Follow-up continued from first record of atrial fibrillation to the end of the study (December 2010). Major bleeding events were recorded, defined as bleeding with a drop in hemoglobin of at least 20 g/L, bleeding requiring transfusion of at least one unit of blood, symptomatic critical organ bleeding, or death from bleeding. A HAS-BLED score was calculated for each subject, as well as a HEMORR2HAGES score, ATRIA score, and bleeding risk scores based on the methods of Beyth et al., Kuijer et al., and Shireman et al., were also calculated for comparison. Predictive value of risk scores was assessed using the c-statistic and net reclassification improvement (NRI). Subjects were classified as low, moderate, and high bleeding risk based on HAS-BLED scores of 0, 1-2, or ≥3, respectively. The authors also performed a Cox regression to identify independent risk factors for bleeding.
The cohort studied consisted of 7,156 subjects with atrial fibrillation, of which 1,054 (17.5%) were high risk, 4,620 (64.6%) were moderate risk, and 1,282 (17.9%) were low risk. Independent predictors of bleeding included age ≥75 years, age ≥65 years, excess alcohol use, anemia, and heart failure. The use of oral anticoagulants did not correlate with HAS-BLED risk category, reported as 46.4%, 59.8%, and 50.1%, in the low, moderate, and high risk categories, respectively. HAS-BLED score predicted risk of stroke or thromboembolism (event rate [ER], 1.24; 95% CI, 1.05-1.45), and stroke or death (ER, 2.70; 95% CI, 2.42-3.01), as well as major bleeding (ER, 1.26; 95% CI, 1.07-1.47), and all-cause mortality (ER, 1.99; 95% CI, 1.75-2.25). Although all risk scores studied were significant predictors of bleeding events, the HAS-BLED score significantly improved NRI compared with other risk scores.
The authors concluded that current oral anticoagulant prescribing patterns would suggest that bleeding risk estimation by clinicians is poor, or that oral anticoagulant prescribing does not reflect bleeding risk per se. The authors also observed that the HAS-BLED score performs well in relation to predicting bleeding events compared to older bleeding scores and the ATRIA score, with significantly improved reclassification.
A great deal of study has addressed clinical predictors of stroke associated with atrial fibrillation, and risk tools to identify patients at increased risk of stroke with atrial fibrillation who therefore warrant anticoagulant therapy. Far less attention has been paid to estimating bleeding risk associated with oral anticoagulant use. The current study uses a large observational registry to compare various published bleeding risk scores. This study suggests that, while all the risk scores predict bleeding risk, the HAS-BLED score performs best. It should be noted, however, that the predictive power of this score is modest (c-statistic about 0.6), and equally effective at predicting bleeding risk whether patients were receiving warfarin or not. This important study provides support for the use of the HAS-BLED score to assess bleeding risk associated with warfarin in atrial fibrillation patients, but also reminds clinicians of the importance of assessing both a given atrial fibrillation patient’s risk of stroke without anticoagulation, as well as the risk of bleeding with anticoagulation, and using both pieces of information to advise patients regarding the propriety of oral anticoagulants in atrial fibrillation.
Keywords: Stroke, Follow-Up Studies, Warfarin, Risk Factors, Blood Transfusion, Thromboembolism, Registries, Blood Coagulation, France, Hemoglobins, Heart Failure, Hemorrhage, Atrial Flutter
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