Bleeding risk in atrial fibrillation (validated in the DOAC era)

What it is and when to use it

The ORBIT score estimates the risk of major bleeding in patients with atrial fibrillation treated with oral anticoagulation (vitamin K antagonists or direct oral anticoagulants). It scores five variables: older age (>74 years), low haemoglobin or anaemia, history of bleeding, renal impairment (estimated GFR <60 ml/min) and concomitant antiplatelet therapy. It was derived and validated in the ORBIT-AF cohort and shows better calibration than some older scores. The 2024 ESC guideline on atrial fibrillation references it among tools for quantifying bleeding risk, with the emphasis on identifying and correcting modifiable risk factors rather than withholding anticoagulation.

How to interpret it

The score ranges from 0 to 7 points. Points are assigned as follows: age >74 years 1, low haemoglobin/anaemia 2, history of bleeding 2, renal impairment (GFR <60) 1, and concomitant antiplatelet therapy 1. It stratifies into three categories: low risk (0-2 points), intermediate risk (3 points) and high risk (4-7 points), with rising rates of major bleeding per 100 patient-years across the bands. A high score does not contraindicate anticoagulation: it should prompt correction of modifiable factors (anaemia, unnecessary antiplatelet, renal function) and closer follow-up.

Limitations and when not to use it

It was validated in patients with atrial fibrillation who were candidates for or already receiving anticoagulation; it should not be applied to non-AF populations or used as an absolute rule to deny anticoagulation. It does not estimate stroke risk or the net benefit of anticoagulation, which must be assessed independently (for example with CHA₂DS₂-VASc). The most frequent misuse is using a high bleeding score to avoid anticoagulating a patient with a clear indication, when the correct approach is to address modifiable factors and reassess periodically.

Frequently asked questions

What is the difference between ORBIT and HAS-BLED?

Both estimate bleeding risk in anticoagulated AF, but ORBIT incorporates objective laboratory parameters (haemoglobin/anaemia and renal function) and shows good calibration; HAS-BLED includes variables such as uncontrolled hypertension and labile INR. They can be used in a complementary way.

Does a high ORBIT score mean anticoagulation should be stopped?

No. A high risk does not contraindicate anticoagulation; it should prompt correction of modifiable factors (anaemia, unnecessary antiplatelet) and closer monitoring, while continuing anticoagulation if indicated by stroke risk.

Which ORBIT values define high risk?

A score of 0-2 indicates low risk, 3 intermediate risk and 4-7 high risk of major bleeding, with increasing rates across each category.