The CHADS₂ score is the original, simple tool for estimating annual stroke risk in patients with non-valvular atrial fibrillation. It is quick to apply and still widely cited, though many guidelines now prefer the more detailed CHA₂DS₂-VASc.
How it works
Each risk factor adds points; prior stroke or TIA is weighted double:
- C — Congestive heart failure (or LV dysfunction): 1 point.
- H — Hypertension: 1 point.
- A — Age 75 years or over: 1 point.
- D — Diabetes mellitus: 1 point.
- S₂ — prior Stroke or TIA: 2 points.
The total ranges from 0 to 6 and maps to an estimated annual stroke rate:
0 -> 1.9% 1 -> 2.8% 2 -> 4.0%
3 -> 5.9% 4 -> 8.5% 5 -> 12.5% 6 -> 18.2%Example and notes
A 78-year-old (1) with hypertension (1) and diabetes (1) but no heart failure or
prior stroke scores 3, corresponding to roughly a 5.9% annual stroke rate —
high enough that anticoagulation is generally recommended after weighing bleeding
risk.
CHADS₂ tends to lump together patients the newer CHA₂DS₂-VASc would separate, so a low CHADS₂ should be confirmed against the more granular score before deciding against anticoagulation. Always balance stroke risk against bleeding risk (for example with HAS-BLED) for the individual patient.
CHADS₂ versus CHA₂DS₂-VASc: what changed and why
The CHADS₂ score was validated in 2001 using a cohort of patients hospitalised for heart failure or seen in practice, and it became the first widely adopted clinical tool for AF stroke risk stratification. However, subsequent research showed that CHADS₂ classified too many patients as “low risk” (score 0 or 1) who subsequently had strokes. The CHA₂DS₂-VASc score, introduced in 2010, addressed this by adding three additional risk factors:
- Vascular disease (prior MI, peripheral arterial disease, or aortic plaque)
- Age 65–74 (a partial point between no-age-factor and the full 75+ point)
- Female sex category (a weak but independently observed risk factor in AF)
These additions better identify truly low-risk patients — specifically men with a CHA₂DS₂-VASc score of 0 — for whom oral anticoagulation may be deferred. Most current guidelines from the European Society of Cardiology and the American Heart Association recommend CHA₂DS₂-VASc for decision-making, with CHADS₂ remaining a useful reference for historical context and quick bedside triage.
Interpreting the result alongside bleeding risk
Stroke risk must always be balanced against bleeding risk before starting anticoagulation. The HAS-BLED score quantifies one-year major bleeding risk in AF patients on anticoagulation, using:
- Uncontrolled hypertension
- Renal or liver dysfunction
- Prior stroke
- Bleeding history or predisposition
- Labile INR (if on warfarin)
- Elderly (age over 65)
- Drugs or alcohol use
A high HAS-BLED score does not rule out anticoagulation — it flags modifiable risk factors to address (such as blood pressure control or medication review) before starting therapy. The clinical decision balances the CHADS₂ or CHA₂DS₂-VASc stroke risk against the bleeding risk, using both scores together.
This tool is a reference aid only. Anticoagulation decisions in individual patients require full clinical assessment by a qualified clinician.