Clinical prediction guide

The ABCD, California, and unified ABCD² risk scores predicted stroke within 2, 7, and 90 days after TIA

Johnston SC, Rothwell PM, Nguyen-Huynh MN, et al. Validation and refinement of scores to predict very early stroke risk after transient ischaemic attack. Lancet 2007;369:283–92.[CrossRef][Medline]

Q In patients with transient ischaemic attack (TIA), how does a new unified risk score (ABCD²) compare with the previously developed ABCD and California scores for predicting 2, 7, and 90 day stroke risk?

Clinical impact ratings GP/FP/Primary care Neurology Internal medicine

Key Words: cerebrovascular accident • ischaemic attack (transient)

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.

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.

View this table: in this window | in a new window   Prevalence and likelihood ratios (LRs) for stroke at 2, 7, and 90 days after a transient ischaemic attack using the unified ABCD2 risk score*

 

The ABCD, California, and unified ABCD² risk scores had similar accuracy for predicting stroke within 2, 7, and 90 days after a transient ischaemic attack.

Abstract and commentary also appear in ACP Journal Club.

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.

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Commentary

Graeme J Hankey, MD

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.

1. Streifler JY, Eliasziw M, Benavente OR, et al. The risk of stroke in patients with first-ever retinal vs hemispheric transient ischemic attacks and high-grade carotid stenosis. North American Symptomatic Carotid Endarterectomy Trial. Arch Neurol 1995;52:246–9.[Abstract/Free Full Text]
2. Hill MD, Yiannakoulias N, Jeerakathil T, et al. The high risk of stroke immediately after transient ischemic attack: a population-based study. Neurology 2004;62:2015–20.[Abstract/Free Full Text]

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