Week 41 – HAS-BLED

 

“A Novel User-Friendly Score (HAS-BLED) To Assess 1-Year Risk of Major Bleeding in Patients with Atrial Fibrillation”

Chest. 2010 Nov;138(5):1093-100. [free full text]

Atrial fibrillation (AF) is a well-known risk factor for ischemic stroke. Stroke risk is further increased by individual comorbidities, such as CHF, HTN, and DM, and can be stratified with scores, such as CHADS2 and CHA2DS2VASC. Patients with intermediate stroke risk are recommended to be treated with oral anticoagulation (OAC). However, stroke risk is often also closely related to bleeding risk, and the benefits of anticoagulation for stroke need to be weighed against the added risk of bleeding. At the time of this study, there were no validated and user-friendly bleeding risk-stratification schemes. This study aimed to develop a practical risk score to estimate the 1-year risk of major bleeding (as defined in the study) in a contemporary, real world cohort of patients with AF.

The study enrolled adults with an EKG or Holter-proven diagnosis of AF. (Patients with mitral valve stenosis or previous valvular surgery were excluded.) No experiment was performed in this retrospective cohort study.

In a derivation cohort, the authors retrospectively performed univariate analyses to identify a range of clinical features associated with major bleeding (p < 0.10). Based on systematic reviews, they added additional risk factors for major bleeding. Ultimately, what resulted was a list of comprehensive risk factors deemed HAS-BLED:

H – Hypertension (> 160 mmHg systolic)

A – Abnormal renal (HD, transplant, Cr > 2.26 mg/dL) and liver function (cirrhosis, bilirubin > 2x normal w/ AST/ALT/ALP > 3x normal) – 1 pt each for abnormal renal or liver function

S – Stroke

B – Bleeding (prior major bleed or predisposition to bleed)

L – Labile INRs (time in therapeutic range < 60%)

E – Elderly (age > 65)

D – Drugs (i.e. ASA, clopidogrel, NSAIDs) or alcohol use (> 8 units per week) concomitantly – 1 pt each for use of either

Each risk factor was equivalent to one point. The HAS-BLED score was then compared to the HEMORR2HAGES scheme, a prior tool for estimating bleeding risk.

Outcomes:

      • incidence of major bleeding within 1 year, overall
      • bleeds per 100 patient-years, by HAS-BLED score
      • c-statistic for the HAS-BLED score in predicting the risk of bleeding

Definitions:

      • major bleeding = bleeding causing hospitalization, Hgb drop >2 g/L, or requiring blood transfusion, that was not a hemorrhagic stroke
      • hemorrhagic stroke = focal neurologic deficit of sudden onset, diagnosed by a neurologist, lasting >24h and caused by bleeding

Results:
3,456 patients with AF without mitral valve stenosis or valve surgery who completed their 1-year follow-up were analyzed retrospectively. 64.8% (2242) of these patients were on OAC (12.8% of whom on concurrent antiplatelet therapy), 24% (828) were on antiplatelet therapy alone, and 10.2% (352) received no antithrombotic therapy. 1.5% (53) of patients experienced a major bleed during the first year, with 17% (9) of these patients sustaining intracerebral hemorrhage.

HAS-BLED Score       Bleeds per 100-patient years
0                                       1.13
1                                       1.02
2                                       1.88
3                                       3.74
4                                       8.70
5                                      12.50
6*                                    0.0                   *(n = 2 patients at risk, neither bled)

Patients were given a HAS-BLED score and a HEMORR2HAGES score. C-statistics were then used to determine the predictive accuracy of each model overall as well as within patient subgroups (OAC alone, OAC + antiplatelet, antiplatelet alone, no antithrombotic therapy).

C statistics for HAS-BLED were as follows: for overall cohort, 0.72 (95%CI 0.65-0.79); for OAC alone, 0.69 (95%CI 0.59-0.80); for OAC + antiplatelet, 0.78 (95%CI 0.65-0.91); for antiplatelet alone, 0.91 (95%CI 0.83-1.00); and for those on no antithrombotic therapy, 0.85 (95%CI 0.00-1.00).

C statistics for HEMORR2HAGES were as follows: for overall cohort, 0.66 (95%CI 0.57-0.74); for OAC alone, 0.64 (95%CI 0.53-0.75); for OAC + antiplatelet, 0.83 (95%CI 0.74-0.91); for antiplatelet alone, 0.83 (95%CI 0.68-0.98); and for those without antithrombotic therapy, 0.81 (95%CI 0.00-1.00).

Implication/Discussion:
This study helped to establish a practical and user-friendly assessment of bleeding risk in AF. HAS-BLED is superior to its predecessor HEMORR2HAGES in that it has an easier-to-remember acronym and is quicker and simpler to perform. All of its risk factors are readily available from the clinical history or are routinely tested. Both stratification tools had a broadly similar c-statistics for the overall cohort – 0.72 for HAS-BLED versus 0.66 for HEMORR2HAGES respectively. However, HAS-BLED was particularly useful when looking at antiplatelet therapy alone or no antithrombotic therapy at all (0.91 and 0.85, respectively).

This study is useful because it provides evidence-based, easily-calculable, and actionable risk stratification in assessing bleeding risk in AF. In prior studies, such as ACTIVE-A (ASA + clopidogrel versus ASA alone for patients with AF deemed unsuitable for OAC), almost half of all patients (n= ~3500) were given a classification of “unsuitable for OAC,” which was based solely on physician clinical judgement alone without a predefined objective scoring. Now, physicians have an objective way to assess bleed risk rather than “gut feeling” or wanting to avoid iatrogenic insult.

The RE-LY trial used the HAS-BLED score to decide which patients with AF should get the standard dabigatran dose (150mg BID) versus a lower dose (110mg BID) for anticoagulation. This risk-stratified dosing resulted in a significant reduction in major bleeding compared with warfarin and maintained a similar reduction in stroke risk.

Furthermore, the HAS-BLED score could allow the physician to be more confident when deciding which patients may be appropriate for referral for a left atrial appendage occlusion device (e.g. Watchman).

Limitations:
The study had a limited number of major bleeds and a short follow-up period, and thus it is possible that other important risk factors for bleeding were not identified. Also, there were large numbers of patients lost to 1-year follow-up. These patients were likely to have had more comorbidities and may have transferred to nursing homes or even have died – which may have led to an underestimate of bleeding rates. Furthermore, the study had a modest number of very elderly patients (i.e. 75-84 and ≥ 85), who are likely to represent the greatest bleeding risk.

Bottom Line:
HAS-BLED provides an easy, practical tool to assess the individual bleeding risk of patients with AF. Oral anticoagulation should be considered for scores of 3 or less. When HAS-BLED scores are ≥ 4, it is reasonable to think about alternatives to oral anticoagulation.

Further Reading/References:
1. HAS-BLED @ 2 Minute Medicine
2. ACTIVE-A trial
3. RE-LY trial
4. RE-LY @ Wiki Journal Club
5. HAS-BLED Calculator
6. HEMORR2HAGES Calculator
7. CHADS2 Calculator
8. CHA2DS2VASC Calculator
9. Watchman (for Healthcare Professionals)
10. “Bleeding Risk Scores in Atrial Fibrillation: Helpful or Harmful?” Journal of the American Heart Association (2018)

Summary by Patrick Miller, MD

Image Credit: CardioNetworks, CC BY-SA 3.0, via Wikimedia Commons

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