The tool to assess the risk of major bleeding in adult patients with atrial fibrillation planned for anticoagulation. ORBIT can be calculated by assessing the presence of the following variables (ORBIT): - O : Older age (1 point if age >74 years) - R : Reduced hemoglobin or hematocrit level (anaemia), hemoglobin (<13 mg/dL for males and <12 mg/dL for females) or hematocrit (<40% for males and <36% for females). Noted that different normal range apply for male and female gender (2 points if present) - B : Bleeding history (history of gastrointestinal bleeding, intracranial bleeding, or hemorrhagic stroke) (2 points if present) - I : Insufficient kidney function, based on the Glomerular Filtration Rate (GFR) (1 point if GFR < 60mL/min/1.73m2) - T: Treatment with antiplatelet agents (1 point if present) Every point contributed by the variable will be summed into the ORBIT score. - Score 0-2 represents the low risk group with 2.4 events of bleed per 100 patient-years. - Score 3 represents the medium risk group with with 4.7 events of bleed per 100 patient-years. - Score 4-7 represents the high risk group with 8.1 events of bleed per 100 patient-years. Patient-years is the number of incident cases divided by the amount of person-time at risk.