HAS-BLED
The HAS-BLED score is a clinical prediction rule designed to estimate the one-year risk of major bleeding in patients with atrial fibrillation who are receiving oral anticoagulation therapy. Developed and validated using data from the Euro Heart Survey on Atrial Fibrillation involving over 3,900 patients, it offers a straightforward method to quantify bleeding risk through seven readily assessable factors, aiding clinicians in balancing thrombotic and hemorrhagic risks.[1] The acronym HAS-BLED represents the following components, each assigned one point unless otherwise specified: Hypertension (uncontrolled systolic blood pressure >160 mmHg), Abnormal renal function (chronic dialysis, renal transplantation, or serum creatinine ≥200 μmol/L [≥2.26 mg/dL]), Stroke (prior history), Bleeding history or predisposition (prior major bleeding or bleeding diathesis, anemia, etc.), Labile INR (unstable/high INRs or time in therapeutic range <60% for those on vitamin K antagonists), Elderly (age >65 years), and Drugs (concomitant antiplatelet agents or nonsteroidal anti-inflammatory drugs) or alcohol (≥8 units/week) concomitantly, with one point each for drugs and alcohol. Abnormal liver function (chronic hepatic disease [e.g., cirrhosis] or significant hepatic derangement [bilirubin >2× upper limit of normal, with AST/ALT/ALP >3× upper limit]) also contributes one point, allowing for a maximum total score of 9.[1][2] A score of 0 corresponds to a low annual major bleeding risk of approximately 1%, increasing progressively to over 12% for scores of 5 or higher, with scores ≥3 indicating high risk and warranting closer monitoring, modifiable risk factor management, and regular review rather than withholding anticoagulation.[1] The tool has been externally validated in multiple cohorts, including those on direct oral anticoagulants, and outperforms older scores like HEMORR₂HAGES and ATRIA in predicting bleeding events, leading to its endorsement in major guidelines such as those from the European Society of Cardiology.[3]Introduction
Definition
The HAS-BLED score is a clinical risk assessment tool designed to estimate the one-year risk of major bleeding events in patients with atrial fibrillation (AF) who are candidates for oral anticoagulation therapy.[1] It was originally published in 2010 as a user-friendly alternative to existing bleeding risk models, derived from data in the Euro Heart Survey on AF involving nearly 4,000 patients.[1] The acronym HAS-BLED expands to represent its seven key risk factors: Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile international normalized ratio, Elderly (age >65 years), and Drugs or alcohol concomitantly.[1] Each component contributes to a simple integer score that quantifies bleeding vulnerability, aiding clinicians in balancing thrombotic and hemorrhagic risks during treatment decisions.[1] In this context, major bleeding is defined as any event involving intracranial hemorrhage, bleeding requiring hospitalization, a hemoglobin decrease greater than 2 g/dL, or the need for blood transfusion.[1] This definition aligns with established criteria for clinically significant bleeds in anticoagulated AF populations, emphasizing outcomes that impact patient morbidity and management.[1]Development and History
The HAS-BLED score was developed in 2010 by a team of researchers including Ron Pisters, Deirdre A. Lane, Robby Nieuwlaat, Cees B. de Vos, Harry J.G.M. Crijns, and Gregory Y.H. Lip, primarily affiliated with institutions in the Netherlands and the United Kingdom. The score was first introduced in the article titled "A novel user-friendly score (HAS-BLED) to assess 1-year risk of major bleeding in patients with atrial fibrillation: the Euro Heart Survey," published in the journal Chest. The development drew from data in the Euro Heart Survey on Atrial Fibrillation (EHS-AF), a multinational observational study conducted by the European Society of Cardiology, which analyzed 3,978 patients with atrial fibrillation who had complete one-year follow-up data. This cohort allowed for the identification and weighting of key bleeding risk factors through univariate and multivariate analyses, enabling the creation of a simple predictive model. The EHS-AF dataset provided a real-world representation of diverse atrial fibrillation patients, many on oral anticoagulation, facilitating both derivation and internal validation of the score. The primary rationale for creating HAS-BLED was to address the absence of a validated, user-friendly tool for quantifying one-year major bleeding risk in atrial fibrillation patients receiving oral anticoagulation, surpassing informal or less structured clinical assessments previously used. Prior to its introduction, bleeding risks were often evaluated ad hoc without standardized quantification, leading to inconsistent decision-making in antithrombotic therapy. HAS-BLED was designed to incorporate readily available clinical and laboratory factors, promoting practical application in routine care to balance thrombotic and bleeding risks. Since its 2010 publication, the HAS-BLED score has undergone no major revisions to its core components or methodology and continues to serve as a standard bleeding risk assessment tool in major guidelines.[4] It remains widely recommended in clinical practice for atrial fibrillation management, with ongoing comparative studies evaluating its performance against newer scores as of 2025.[5]Components and Scoring
Risk Factors
The HAS-BLED score assesses bleeding risk in patients with atrial fibrillation, particularly those on oral anticoagulation, through an acronym representing eight key modifiable and non-modifiable risk factors. Each factor is assigned 1 point if present, yielding a total score from 0 to 9, though the categories for abnormal renal/liver function and drugs/alcohol can contribute up to 2 points each. These criteria were derived from the Euro Heart Survey on atrial fibrillation and validated in a cohort of 3,978 patients.[1] Hypertension (H) refers to uncontrolled high blood pressure, specifically a systolic blood pressure greater than 160 mm Hg. This threshold indicates poor blood pressure management, which can exacerbate vascular fragility and increase bleeding propensity in anticoagulated patients.[1] Abnormal renal function (A) is defined by the presence of chronic dialysis, prior renal transplantation, or serum creatinine levels of 200 µmol/L (equivalent to ≥2.26 mg/dL) or higher. These indicators reflect significant impairment in kidney function, which can alter drug metabolism and heighten bleeding risks due to uremic platelet dysfunction. Abnormal liver function, also under this category, includes chronic hepatic disease such as cirrhosis or biochemical abnormalities like bilirubin more than twice the upper limit of normal, alongside aspartate aminotransferase (AST), alanine aminotransferase (ALT), or alkaline phosphatase (ALP) levels exceeding three times the upper limit of normal; each subcomponent scores 1 point, for a maximum of 2 in this category.[1] Stroke (S) encompasses any prior history of stroke, signifying underlying cerebrovascular vulnerability that may compound bleeding hazards during anticoagulation therapy.[1] Bleeding history or predisposition (B) involves a previous major bleeding event or conditions predisposing to hemorrhage, such as anemia or other bleeding diatheses. Major bleeding is typically defined as intracranial hemorrhage, hospitalization, hemoglobin drop greater than 2 g/dL, or transfusion requirement, highlighting patients at elevated risk for recurrent events.[1] Labile international normalized ratio (L) denotes unstable or elevated international normalized ratios (INRs) in patients on vitamin K antagonists, specifically when the time in therapeutic range is less than 60%. This instability reflects suboptimal anticoagulation control, which correlates with fluctuating bleeding and thrombotic risks.[1] Elderly (E) applies to patients aged older than 65 years, as advanced age is associated with frailty, reduced physiological reserve, and higher susceptibility to bleeding complications independent of other factors.[1] Drugs (D) includes concomitant use of antiplatelet agents (e.g., aspirin or clopidogrel) or nonsteroidal anti-inflammatory drugs (NSAIDs), which can synergistically increase bleeding risk when combined with anticoagulants; this subcomponent scores 1 point. Alcohol refers to excessive consumption, defined as 8 or more standard units per week, which may impair liver function, coagulation, and medication adherence, also scoring 1 point for a maximum of 2 in this category.[1]Calculation
The HAS-BLED score is computed by summing one point for each applicable risk factor present in the patient, with the acronym representing hypertension (H), abnormal renal or liver function (A), stroke (S), bleeding history or predisposition (B), labile international normalized ratio (L), elderly age (E), and concomitant drugs or alcohol use (D).[1] Abnormal renal or liver function contributes up to two points if both are present: one point for renal criteria (chronic dialysis, renal transplantation, or serum creatinine ≥ 200 µmol/L) and one for liver criteria (chronic hepatic disease or biochemical evidence such as bilirubin > 2 × upper limit of normal, or aspartate aminotransferase/alanine aminotransferase/alkaline phosphatase > 3 × upper limit of normal).[1] Similarly, concomitant drugs or alcohol use can contribute up to two points: one for predisposing drugs (e.g., antiplatelet agents or nonsteroidal anti-inflammatory drugs) and one for excessive alcohol consumption (≥8 units per week).[1] The remaining components each contribute a single point if present: uncontrolled hypertension (systolic blood pressure > 160 mm Hg); prior stroke; bleeding history or predisposition (e.g., prior major bleeding or anemia); labile INR (time in therapeutic range < 60%); and age > 65 years.[1] The total score ranges from 0 to 9 points, calculated as the simple sum of these assigned points (e.g., HAS-BLED = H + A_renal + A_liver + S + B + L + E + D_drugs + D_alcohol).[1] For example, a patient with uncontrolled hypertension, age > 65 years, and excessive alcohol use would receive 1 point for H, 1 point for E, and 1 point for D (alcohol), resulting in a total score of 3.[1]Clinical Application
Interpretation of Scores
The HAS-BLED score categorizes patients with atrial fibrillation into risk levels for major bleeding over one year, primarily based on validation in the Euro Heart Survey cohort. Scores of 0-1 indicate low risk, with an annual major bleeding rate of approximately 1% (0.6% for score 0 and 1.5% for score 1).[1] A score of 2 denotes moderate risk, associated with an annual major bleeding rate of around 2-3%.[1] Scores of 3 or higher signify high risk, with annual major bleeding rates ranging from 3% to 9% or more, escalating with each additional point (e.g., up to 8.9% for scores ≥5 in broader validations).[1] In the original validation study, the risk of major bleeding demonstrated a significant increasing trend with higher HAS-BLED scores (p < 0.001), with each one-point increment linked to a hazard ratio of approximately 1.47 for bleeding events.[1] This predictive pattern holds across subgroups, including those on antiplatelet therapy alone (C-statistic 0.91) or no antithrombotic therapy (C-statistic 0.85), underscoring the score's utility in estimating relative risk escalation.[1] A high HAS-BLED score (≥3) signals the need for caution in anticoagulation management but does not contraindicate therapy, as the net clinical benefit often favors continuation after balancing stroke risk. Instead, it prompts proactive addressing of modifiable risk factors, such as optimizing blood pressure control, stabilizing INR, minimizing concomitant drugs or alcohol use, to mitigate bleeding potential while maintaining protective anticoagulation.[1] Regular reassessment of the score is recommended to reflect changes in patient status.| HAS-BLED Score | Risk Level | Approximate Annual Major Bleeding Rate (%) |
|---|---|---|
| 0-1 | Low | ~1 |
| 2 | Moderate | ~2-3 |
| ≥3 | High | 3-9+ (increases per point) |