CHASE-LESS Score Calculator
Enter age and stroke severity and select applicable items — the score is calculated below immediately.
Result
Score: —
Interpretation following Hsieh et al., 2020: —
How to interpret the CHASE-LESS score
The original publication groups the total score into four risk categories. The incidence of newly diagnosed atrial fibrillation (AF) within one year after ischemic stroke rose steeply across them:
| CHASE-LESS score | Risk category | Share of patients | Newly diagnosed AF per 1000 person-years | Number needed to screen per year |
|---|---|---|---|---|
| 1–3 | Low | 6.8% | 8.3 | 120 |
| 4–6 | Low intermediate | 44.3% | 24.0 | 42 |
| 7–9 | High intermediate | 34.7% | 68.3 | 15 |
| ≥ 10 | High | 14.1% | 240.4 | 4 |
Overall, 6.0% of patients were diagnosed with AF within one year (60.7 per 1000 person-years; number needed to screen 16). The authors suggest that the score can help prioritise patients for prolonged cardiac monitoring, for example by reserving long-term ECG monitoring for patients with a high score and a negative 24-hour Holter ECG.
What is the CHASE-LESS score?
The CHASE-LESS score (Coronary, Heart failure, Age, stroke SEverity − LipidEmia, Sugar, prior Stroke) predicts newly diagnosed AF within one year after ischemic stroke in patients without known AF. It was developed by Cheng-Yang Hsieh, Cheng-Han Lee and Sheng-Feng Sung and published in 2020.
The score was derived from Taiwan's National Health Insurance Research Database. It included 17,076 adults hospitalised for ischemic stroke between 2000 and 2013 without known AF or prior oral anticoagulation. Patients were randomly split into a development cohort (two thirds) and a validation cohort (one third). The c-index was 0.730 in the development cohort and 0.732 in the validation cohort. In the validation cohort, this was significantly higher than for the AS5F score (0.709), the C2HEST score (0.615), the CHA2DS2-VASc score (0.578) and the CHADS2 score (0.536).
Scoring table
| Item | Points |
|---|---|
| Age | +1 per 10 years |
| Stroke severity: NIHSS 6–13 | +1 |
| Stroke severity: NIHSS ≥ 14 | +4 |
| Coronary artery disease | +1 |
| Congestive heart failure | +1 |
| Hyperlipidemia | −1 |
| Diabetes mellitus | −1 |
| Prior stroke or transient ischemic attack | −1 |
The points were derived by dividing each regression coefficient by the coefficient for 10 years of age. In the study population, total scores ranged from 1 to 15, with a median of 6.
Example: a 72-year-old patient (7 points) with an NIHSS of 8 (1 point) and diabetes (−1 point) has a score of 7, which corresponds to the high intermediate category.
Limitations
- The score was developed from insurance claims data. Comorbidities were identified by diagnosis codes, and AF may have been under-diagnosed or incompletely coded, because long-term cardiac monitoring was not used routinely.
- Stroke severity was not recorded in the database. The NIHSS was estimated from a claims-based stroke severity index rather than measured.
- The type of ischemic stroke was not available, and sex differences in AF risk were not addressed.
- The score was developed and validated in a Taiwanese population, using a random split of the same database.
Frequently asked questions
Why do diabetes, hyperlipidemia and prior stroke subtract points?
These are risk factors for stroke itself. According to the authors, patients who have them need no occult AF to explain their stroke, so AF is found less often among them. This resembles index event bias. It also explains why CHADS2 and CHA2DS2-VASc, which count diabetes and prior stroke as positive predictors, performed poorly for this purpose.
How are age points counted?
The publication assigns 1 point for every 10 years of age. This calculator counts completed decades, so a 72-year-old patient receives 7 points.
What if the calculated score is below 1?
In the original study population, scores ranged from 1 to 15. A score below 1 is outside this range. The calculator then shows the lowest risk category.
How does CHASE-LESS differ from AF-ESUS and C2HEST?
CHASE-LESS was developed in unselected patients with ischemic stroke and uses only clinical data available on admission. The AF-ESUS score was developed for embolic stroke of undetermined source and also requires echocardiography, ECG and imaging findings. The C2HEST score was designed for the general population and does not include stroke severity.
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Reference
Hsieh CY, Lee CH, Sung SF. Development of a novel score to predict newly diagnosed atrial fibrillation after ischemic stroke: the CHASE-LESS score. Atherosclerosis. 2020;295:1–7. doi:10.1016/j.atherosclerosis.2020.01.003
Written and medically reviewed by Frederic Eberhardt, MD. Last reviewed: 13 October 2026