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Clinical prediction guide |
Clinical impact ratings GP/FP/Primary care
Neurology Internal medicine
Key Words: cerebrovascular accident • ischaemic attack (transient)
METHODS
Design:
6 cohort studies: 2 derivation cohorts (California emergency department [ED] and Oxford population) and 4 independent validation cohorts (California ED, California clinic, Oxford population, and Oxford clinic).
Setting:
EDs and primary care clinics in the San Francisco Bay area, California, USA and family practices and specialist clinics in Oxfordshire, UK.
Patients:
1916 patients (78% >60 y, 52% women) for derivation and 2893 patients (76% >60 y, 53% women) for validation who were diagnosed with TIA by the initial treating doctor.
Description of prediction guide:
The ABCD2 score was generated in the 2 original derivation cohorts by multivariate logistic regression analysis of individual risk factors from the ABCD and California scores. The risk score with the greatest area under the receiver operating characteristic (AUROC) curve for 2 day stroke was selected. The unified ABCD2 score (range 0–7) was a summation of 5 independent risk predictors: Age (
60 y = 1), Blood pressure (systolic 140 mm Hg or diastolic 90 mm Hg = 1), Clinical features (focal weakness = 2, speech impairment without focal weakness = 1), Duration of symptoms (60 min = 2, 10–59 min = 1), and Diabetes = 1.
Outcomes:
2, 7, and 90 day risk of stroke.
MAIN RESULTS
Overall, 3.9%, 5.5%, and 9.2% of patients had stroke within 2, 7, and 90 days of TIA, respectively. The ABCD2, ABCD, and California risk scores did not differ for prediction of 2, 7, or 90 day stroke (AUROC curve 0.62–0.83 v 0.62–0.81 v 0.60–0.79). For the ABCD2 risk score, the prevalence and likelihood ratios for 2, 7, and 90 day stroke in the 2 derivation and 4 validation cohorts combined are in the table 
. In all 6 cohorts, the ABCD2 score classified 34%, 45%, and 21% of patients as low (score 0–3), moderate (score 4–5), and high (score 6–7) risk of stroke, respectively.
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Abstract and commentary also appear in ACP Journal Club.
FOOTNOTES
For correspondence: Dr S C Johnston, University of California, San Francisco, CA, USA. clay.johnston{at}ucsfmedctr.org
Sources of funding: National Institutes of Health; American Heart Association; UK Stroke Association; BUPA Foundation; UK Medical Research Council.
Royal Perth Hospital,
Perth, Western Australia, Australia
Identification of patients at highest and lowest risk of stroke may allow effective yet costly or risky investigations, interventions, and hospital admissions to be targeted to those at highest risk and presumably most likely to benefit. 2 prognostic scores have been proposed: the ABCD score to predict risk of stroke at 7 days and the California score to predict risk of stroke at 90 days.
In the study by Johnston et al, both scores were externally validated (generalisable) for predicting stroke risk at 2, 7, and 90 days in 4 independent cohorts of patients with TIA. Moreover, the study showed that a new unified score, ABCD2, based on 5 clinical factors had somewhat greater predictive value. The validity of the ABCD2 score is also supported by other studies that identified increasing age, limb weakness, and diabetes as risk factors of stroke after TIA.1,2 Some aspects of the ABCD2 score (eg, unilateral weakness, speech impairment, and prolonged duration TIA) probably have prognostic value because they improve the diagnosis of TIA from non-TIA disorders (eg, syncope or migraine). The other features that are important vascular risk factors (increasing age, high blood pressure, and diabetes) are likely to be relevant to the cause of future stroke.
Although additional risk factors not collected from the derivation cohorts might augment the predictive accuracy of the ABCD2 score (eg, frequent TIAs, symptomatic large artery disease, and new ischaemic lesions on brain imaging), the new ABCD2 score is the most externally valid prediction tool currently available. It is ready for use in clinical practice and can be used to triage patients into low (1% 2 d risk), moderate (4%), and high risk (8%) groups. Patients classified at high risk should be prioritised for immediate evaluation, targeted intervention, and perhaps inpatient observation to minimise their risk of future stroke and maximise their chances of access to early thrombolysis (and thereby improved survival free of handicap), should a stroke occur in the next few days.
REFERENCES
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