CHADS2 score: how the points are calculated
The CHADS2 score adds up points for five items in a person with atrial fibrillation: congestive heart failure (1 point), hypertension (1), age 75 or older (1), diabetes (1), and a prior stroke or transient ischemic attack (2). The total runs from 0 to 6. A 78-year-old with hypertension and diabetes and no other items scores 3.
Not a medical device. Not a diagnosis or dosing recommendation.
What is the CHADS2 score?
CHADS2 is a point score for stroke risk in atrial fibrillation, published by Brian Gage and colleagues in JAMA in 2001. The name comes from the items: Congestive heart failure, Hypertension, Age 75 or older, Diabetes, and prior Stroke or TIA, which counts 2 points.
It's also written CHADS₂, and sometimes called the Gage 2001 score or the AF stroke score.
This page explains the arithmetic. It doesn't give a cutoff, it doesn't turn a score into a stroke rate, and it doesn't say what a score means for a particular person.
The CHADS2 formula
CHADS2 = CHF (1) + hypertension (1) + age ≥ 75 (1) + diabetes (1) + prior stroke/TIA (2)
maximum = 6Exact expression the calculator uses:
CHADS2 = CHF 1 + hypertension 1 + age≥75 1 + diabetes 1 + stroke/TIA 2; max 6What each part means
| Item | Plain-English meaning | Points if present |
|---|---|---|
chf | Congestive heart failure or left ventricular dysfunction | 1 |
hypertension | A history of high blood pressure | 1 |
age | Age in years; 75 or older earns the point | 1 |
diabetes | Diabetes mellitus | 1 |
stroke_tia | A prior stroke or transient ischemic attack (TIA) | 2 |
How the score works
- Answer each yes/no item. Heart failure, hypertension, diabetes, and prior stroke or TIA are each yes or no.
- Check age. Enter age in whole years. 75 and over earns 1 point; 74 earns nothing.
- Add the points. Each yes is 1 point, except prior stroke or TIA, which is 2.
- The total is 0 to 6.
Whole numbers
Every item is worth a whole number of points, so the total is always a whole number. Magent's calculator takes age from 18 to 120 and returns the total, the maximum of 6, the age used, and a line for each item showing whether it scored.
Worked examples
These use Magent's own expected values for the calculator.
Example 1: no items
- Age 40; no heart failure, hypertension, diabetes, or prior stroke or TIA.
- Score = 0.
Example 2: age 78 with hypertension and diabetes
- Age 78 is 75 or older → 1.
- Hypertension → 1; diabetes → 1.
- Score = 1 + 1 + 1 = 3.
Example 3: prior stroke or TIA alone
- Age 50; prior stroke or TIA → 2.
- Score = 2.
Example 4: age 74 versus 75
- Age 74, no other items → 0.
- Age 75, no other items → 1.
Example 5: every item
- Age 80 → 1; heart failure → 1; hypertension → 1; diabetes → 1; prior stroke or TIA → 2.
- Score = 6, the maximum.
CHADS2 points table
| Item | No | Yes |
|---|---|---|
| Congestive heart failure | 0 | 1 |
| Hypertension | 0 | 1 |
| Age 75 or older | 0 | 1 |
| Diabetes | 0 | 1 |
| Prior stroke or TIA | 0 | 2 |
| Highest possible total | 6 |
CHADS2 combination table
Each row is one of Magent's expected values for the calculator.
| Age | Heart failure | Hypertension | Diabetes | Stroke/TIA | Score |
|---|---|---|---|---|---|
| 40 | No | No | No | No | 0 |
| 74 | No | No | No | No | 0 |
| 75 | No | No | No | No | 1 |
| 50 | No | No | No | Yes | 2 |
| 78 | No | Yes | Yes | No | 3 |
| 80 | Yes | Yes | Yes | Yes | 6 |
History of the CHADS2 score
The score comes from Brian F. Gage, Amy D. Waterman, William Shannon and colleagues, Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation, JAMA 2001 (volume 285, issue 22, pages 2864–2870).
The abstract explains that two existing classification schemes, from the Atrial Fibrillation Investigators and from the Stroke Prevention in Atrial Fibrillation III study, were combined into the new CHADS2 index. It was formed by assigning 1 point each for congestive heart failure, hypertension, age 75 years or older, and diabetes, and 2 points for a history of stroke or TIA.
The authors tested it in the National Registry of Atrial Fibrillation: 1,733 Medicare beneficiaries aged 65 to 95, from 7 states, who had nonrheumatic atrial fibrillation and weren't prescribed warfarin when they left the hospital.
When it's used
The 2001 abstract describes CHADS2 as a way to quantify the risk of stroke for people who have atrial fibrillation. The National Registry data it was tested on came from people with nonrheumatic atrial fibrillation.
Where it's used
The original registry drew on Medicare data from 7 US states, and stroke admissions were found from Medicare claims data. The 2001 paper compared CHADS2 against the two older schemes it was built from in that same group.
Who uses it
The record says the inputs are yes/no items supplied by the person using the calculator. The calculator doesn't read a chart or decide whether someone has heart failure or a prior stroke; the user does.
Limits of the calculation
- It adds up five items. It doesn't diagnose anything and doesn't give a stroke rate.
- It's the 2001 score as published. The record notes that CHA2DS2-VASc replaced CHADS2 in many guidelines.
- Yes/no items come from the user. Nothing is inferred from notes.
- Age is entered in whole years; the age point starts at 75.
- This page doesn't say what to do with a score.
Clinical decisions belong to a qualified clinician who knows the patient.
Glossary
- Atrial fibrillation (AF): an irregular heart rhythm in the upper chambers of the heart.
- Congestive heart failure: the heart doesn't pump well enough for the body's needs.
- Left ventricular dysfunction: reduced pumping by the heart's main chamber.
- TIA (transient ischemic attack): a brief stroke-like episode whose symptoms resolve.
- Hypertension: high blood pressure.
Common mistakes
- Giving prior stroke or TIA 1 point. It's worth 2.
- Scoring age 65–74. CHADS2 has no point for that range; that's CHA2DS2-VASc.
- Mixing up CHADS2 and CHA2DS2-VASc totals. They have different items and different maximums.
- Counting age 74 as 75. The point starts at 75.
Source
Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA. 2001;285(22):2864-2870. DOI: 10.1001/jama.285.22.2864
Frequently asked questions
How do you calculate a CHADS2 score?
Give 1 point each for congestive heart failure, hypertension, age 75 or older, and diabetes, and 2 points for a prior stroke or TIA. Add them up for a total from 0 to 6.
What CHADS2 score needs a blood thinner?
This page doesn't give a cutoff and doesn't say what to do with a score. It adds up the points; what a score means depends on the person and the clinical context.
What does CHADS2 stand for?
Congestive heart failure, Hypertension, Age 75 or older, Diabetes, and prior Stroke or TIA, with the 2 marking that stroke or TIA counts double.
Does age 65 count in CHADS2?
No. CHADS2 gives its age point at 75 or older. There's no point for ages 65 to 74; that point belongs to CHA2DS2-VASc.
What is the highest CHADS2 score?
6, when every item is present.
Who developed the CHADS2 score?
Brian Gage and colleagues, in a 2001 JAMA paper.