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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
Author Affiliations: Divisions of General Medical Sciences (Drs Gage, Waterman, and Shannon) and Cardiology (Dr Rich), Washington University School of Medicine, St Louis, Mo; Innovative Emergency Management Inc, Baton Rouge, La (Dr Boechler); and Center for Outcomes Research and Evaluation, Yale–New Haven Hospital, New Haven, Conn (Dr Radford).
Context Patients who have atrial fibrillation (AF) have an increased risk of
stroke, but their absolute rate of stroke depends on age and comorbid conditions.
Objective To assess the predictive value of classification schemes that estimate
stroke risk in patients with AF.
Design, Setting, and Patients Two existing classification schemes were combined into a new stroke-risk
scheme, the CHADS2 index, and all 3 classification schemes were
validated. The CHADS2 was formed by assigning 1 point each for
the presence of congestive heart failure, hypertension, age 75 years or older,
and diabetes mellitus and by assigning 2 points for history of stroke or transient
ischemic attack. Data from peer review organizations representing 7 states
were used to assemble a National Registry of AF (NRAF) consisting of 1733
Medicare beneficiaries aged 65 to 95 years who had nonrheumatic AF and were
not prescribed warfarin at hospital discharge.
Main Outcome Measure Hospitalization for ischemic stroke, determined by Medicare claims data.
Results During 2121 patient-years of follow-up, 94 patients were readmitted
to the hospital for ischemic stroke (stroke rate, 4.4 per 100 patient-years).
As indicated by a c statistic greater than 0.5, the
2 existing classification schemes predicted stroke better than chance: c of 0.68 (95% confidence interval [CI], 0.65-0.71) for
the scheme developed by the Atrial Fibrillation Investigators (AFI) and c of 0.74 (95% CI, 0.71-0.76) for the Stroke Prevention
in Atrial Fibrillation (SPAF) III scheme. However, with a c statistic of 0.82 (95% CI, 0.80-0.84), the CHADS2 index
was the most accurate predictor of stroke. The stroke rate per 100 patient-years
without antithrombotic therapy increased by a factor of 1.5 (95% CI, 1.3-1.7)
for each 1-point increase in the CHADS2 score: 1.9 (95% CI, 1.2-3.0)
for a score of 0; 2.8 (95% CI, 2.0-3.8) for 1; 4.0 (95% CI, 3.1-5.1) for 2;
5.9 (95% CI, 4.6-7.3) for 3; 8.5 (95% CI, 6.3-11.1) for 4; 12.5 (95% CI, 8.2-17.5)
for 5; and 18.2 (95% CI, 10.5-27.4) for 6.
Conclusion The 2 existing classification schemes and especially a new stroke risk
index, CHADS2, can quantify risk of stroke for patients who have
AF and may aid in selection of antithrombotic therapy.
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