ATRIA Bleeding Risk Score
The ATRIA study sought to develop a risk stratification score to predict warfarin-associated hemorrhage. Included patients from the Kaiser Permanente of Northern California hospital system with non-valvular, non-transient atrial fibrillation via their ICD-9 codes and then followed up for a period of six to seven years. Patients randomly divided into split-sample “derivation” and “validation” cohorts, in a 2:1 ratio, respectively. The study sought to identify risk factors for patients with major hemorrhage, defined as fatal, requiring transfusion of ≥ 2 units pRBCs, or hemorrhage into critical anatomic site (intracranial, retroperitoneal, etc). Five variables were derived after statistical analysis and then weighed based on degree of effect. Scoring system consisted of five criteria, each of which was worth 1, 2, or 3 points. Study used ≤ 3 points to define low probability group (<1%) for major hemorrhage, 4 points for immediate (2.6%) and 5-10 points for high (5.8%). Points to keep in mind: Patients at risk for major hemorrhage, e.g. those with past intracranial bleeds, were likely already pre-excluded by clinicians and thus not included in the study
Details Formula Study characteristics Files & References
Model author
Model ID
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MeSH terms
  • Atrial Fibrillation
  • Warfarin
  • Model type
    Linear model (Calculation)
    No rating criteria met
    No Formula defined yet
    Condition Formula

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    Study Population

    Total population size: 0

    Additional characteristics

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    ATRIA Bleeding Risk Score
    Refer to Intended Use for instructions before use
    Evidencio B.V., Irenesingel 19, 7481 GJ, Haaksbergen, the Netherlands

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    ATRIA Bleeding Risk Score

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    Outcome stratification

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    Result interpretation

    Determines bleeding risk for patients on warfarin.

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    Calculations alone should never dictate patient care, and are no substitute for professional judgement. See our full disclaimer.

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