A clinical prediction rule to identify patients with atrial fibrillation and a low risk for stroke while taking aspirin.
BACKGROUND
We sought to derive and internally validate a simple and easily applied clinical prediction rule to identify patients with nonvalvular atrial fibrillation (AF) whose stroke risk while taking aspirin is, irrespective of age, low enough that oral anticoagulation therapy is unnecessary.


METHODS
We included 2501 patients with AF treated with aspirin during participation in 6 clinical trials. Patients were randomly divided into derivation and validation sets. Recursive partitioning was used to identify patients in the derivation set whose risk for stroke (ischemic or hemorrhagic) or transient ischemic attack was comparable to that observed in an age- and sex-matched cohort from the Framingham Heart Study. The derived prediction rules were tested on the validation set.


RESULTS
Overall, 166 patients (6.6%) had an event during 4688.6 person-years (PYs) of observation for an incident rate of 3.5 events per 100 PYs. Patients in the derivation set classified as low risk (no previous stroke or transient ischemic attack, no treated hypertension or systolic blood pressure equal to or exceeding 140 mm Hg, no symptomatic coronary artery disease, and no diabetes) experienced 1.0 events per 100 PYs, compared with an age- and sex-matched rate of 1.2 events per 100 PYs. In the validation set, low-risk patients experienced 1.1 events per 100 PYs (expected rate of 1.2 events per 100 PYs). Low-risk patients made up 24% of the cohort and 16% of patients older than 75 years. Low-risk patients who were randomized to therapeutic oral anticoagulation therapy experienced 1.5 events per 100 PYs.


CONCLUSIONS
Irrespective of age, patients with AF and none of these 4 clinical features and who take aspirin have stroke rates comparable to those of age-matched community cohorts and would not benefit substantially from anticoagulation.
van Walraven
Carl
C
Clinical Epidemiology Unit, Ottawa Health Research Institute, Ottawa Hospital, Ontario, Canada. carlv@ohri.ca
Hart
Robert G
RG
Wells
George A
GA
Petersen
Palle
P
Koudstaal
Peter J
PJ
Gullov
Annette L
AL
Hellemons
Beppie S P
BS
Koefed
Birgitte G
BG
Laupacis
Andreas
A
D001241:Aspirin / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy; D002986:Clinical Trials as Topic; D003661:Decision Support Techniques; D005343:Fibrinolytic Agents / Q000627:therapeutic use*; D006305:Health Status Indicators; D006801:Humans; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D020521:Stroke / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D016896:Treatment Outcome
D005343:Fibrinolytic Agents; D001241:Aspirin