CHADS2 score

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CHADS Score or CHADS2 Score is an clinical prediction rule for estimating the risk of stroke in patients with atrial fibrillation (AFIB), a common and usually benign heart arrythmia. It is used to determine the degree of anticoagulation therapy required, since AFIB can cause the stasis of blood in the heart chambers, leading to the formation of a mural thrombus that can dislodge into the blood flow, reaching the brain and causing a stroke. A high CHADS score corresponds to a greater risk, and vice-versa. The CHADS/CHADS2 algorithm was validated by a cohort study published in JAMA in 2001 using 1,733 Atrial fibrillation patients tracked through Medicare claims.

Algorithm

The CHADS/CHADS2 algorithm is as follows:

C:	Congestive heart failure	= 1 point
H:	Hypertension (systolic >160 mmHg)	= 1 point
A:	Age >75 years	= 1 point
D:	Diabetes	= 1 point
S:	Prior Transient ischemic attack or Stroke	= 2 points

Risk of Stroke

According to the findings of the JAMA study, the risk of stroke as a percentage per year is:

Score	Risk of Stroke Per Year	95% CIs from JAMA Study
0	1.9%
1	2.8%
2	4.0%
3	5.9%
4	8.5%
5	12.5%
6	18.2%

Recommendations for Anticoagulation

The following treatment strategies were recommended by the authors of theJAMA and Circulation articles:

Score	Risk	Anticoagulation Therapy	Considerations
0	Low	Aspirin	325 mg/day most likely to offer benefit, although lower doses may be similarly efficacious
1-2	Moderate	Aspirin or Warfarin	Raise INR to 2.0-3.0, depending on factors such as patient preference
3+	High	Warfarin	Raise INR to 2.0-3.0, unless contraindicated (e.g., history of falls, clinically significant GI bleeding, inability to obtain regular INR screening)

Criticism of CHADS

The main criticism of the CHADS/CHADS2 scoring system is that someone with atrial fibrillation and a previous history of stroke, but no other risk factors (i.e. CHADS2 Score = 2), is only classified as moderate risk, whereas that person is in fact at high risk of another stroke.