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Published on: February 28, 2012
Comparative performance of stroke risk scores in patients with atrial fibrillation with low stroke risk
Nicolas Zubrzycki1, Karice Hyun2,3, Erdahl Teber2,3
1St Vincent's Hospital Sydney, Darlinghurst, New South Wales, Australia nzubrz@gmail.com.
Insights
Australian stroke risk scores for atrial fibrillation (AF) need local validation. The CHA2DS2-VA score performed poorly, suggesting a need for new, Australia-specific tools to accurately identify low-stroke-risk patients.
Area of Science:
- Cardiology
- Public Health
- Epidemiology
Background:
- Australian guidelines use the CHA2DS2-VA score to identify low-risk atrial fibrillation (AF) patients who may not need oral anticoagulation.
- Current risk thresholds are based on international data; validation in Australian populations is needed.
- Existing scores (CHADS2, CHA2DS2-VA, ATRIA, Modified-CHADS2) were evaluated for their accuracy in identifying truly low-risk Australian AF patients.
Purpose of the Study:
- To evaluate the accuracy of existing stroke risk scores in identifying truly low-risk patients with atrial fibrillation in Australia.
- To assess whether current risk stratification tools align with Australian patient data for stroke risk.
- To inform the development of locally relevant risk assessment tools for AF management.
Main Methods:
- A population-based cohort study utilized linked New South Wales health and pharmaceutical data.
- Oral anticoagulant-naïve patients with a first AF admission (July 2003 - January 2021) were followed for at least 12 months.
- Predictive accuracy of CHADS2, CHA2DS2-VA, ATRIA, and Modified-CHADS2 scores was assessed using the concordance statistic, defining 'truly low-risk' as <0.9% annual ischemic stroke incidence.
Main Results:
- Over 224,000 patients were analyzed; 1.6% experienced ischemic stroke within 12 months.
- The proportion of patients classified as low-risk varied significantly by score, from 2.0% (Modified-CHADS2) to 50.9% (ATRIA).
- All scores, including CHA2DS2-VA intermediate-risk, identified patients with stroke incidence below the 0.9% threshold. CHA2DS2-VA showed the weakest discrimination (0.61), while ATRIA performed best (0.66).
Conclusions:
- The guideline-recommended CHA2DS2-VA score demonstrated the lowest predictive accuracy in this Australian cohort.
- Patients classified as intermediate-risk by CHA2DS2-VA had stroke incidence below the treatment threshold, indicating potential under-treatment.
- Development and validation of locally applicable stroke risk tools for Australian AF patients are strongly recommended.
Background:
Australian guidelines recommend the CHA2DS2-VA (congestive heart failure, hypertension, age ≥75 years (double weight), diabetes mellitus, previous stroke (double weight), vascular disease, age 65-74 years) score to identify patients with atrial fibrillation (AF) at low stroke risk who should avoid oral anticoagulation. Treatment thresholds were derived from heterogeneous international data, and alternate scores require validation in an Australian population. We evaluated whether existing stroke scores (CHADS2 (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, previous stroke (double weight)), CHA2DS2-VA, ATRIA (anticoagulation and risk factors in atrial fibrillation) and Modified-CHADS2) accurately identify truly low-risk patients in Australia.
Methods:
We conducted a population-based cohort study using linked data from the New South Wales Admitted Patient Data Collection, the National Death Index and the Pharmaceutical Benefits Scheme databases. Oral anticoagulant-naïve patients with a first hospital admission for AF between July 2003 and January 2021 were included. Patients were followed for ≥12 months and classified into low-risk, intermediate-risk or high-risk categories for each score. 'Truly low-risk' was defined as annual ischaemic stroke incidence <0.9%. Predictive accuracy was assessed using the concordance-statistic.
Results:
Among 224 451 eligible patients, 3552 (1.6%) were hospitalised for ischaemic stroke within 12 months. The proportion labelled low-risk ranged from 2.0% (Modified-CHADS2) to 50.9% (ATRIA). Patients assigned low-risk using each score, and intermediate-risk with the CHA2DS2-VA score, met the definition of truly low-risk. Concordance-statistics were modest, with the weakest performing score being the CHA2DS2-VA score (0.61, 95% CI 0.60 to 0.61) and the best performing model being the ATRIA score (0.66, 95% CI 0.66 to 0.67).
Conclusions:
The guideline-endorsed CHA2DS2-VA score showed the lowest discrimination, and patients classified as intermediate-risk using this score had stroke incidence below the treatment threshold. Strong consideration should be given to the development and validation of locally applicable risk tools.
