Fast track — ArticlesRisk of stroke early after transient ischaemic attack: a systematic review and meta-analysis
Introduction
Up to 23% of strokes are preceded by transient ischaemic attack (TIA),1 and there is substantial research interest in improving prevention during the short window between TIA and stroke.2 However, the prospective estimation of the early risk of stroke is logistically difficult and studies have yielded inconsistent results,3 with 7-day risks ranging from 0% to 12·8%.4, 5 Nevertheless, reliable estimation of this risk is essential to allow us to understand the potential absolute benefits of early treatment and the likely cost-effectiveness of different methods of service provision, to inform future clinical trial design, and to justify investment in public education.
The measured risk will depend on several factors. First, study method is important, particularly the delay from TIA to study entry, the inclusion or exclusion of patients having a stroke during this interval, and the thoroughness of follow-up used to identify subsequent stroke.6 Second, the clinical setting (population, emergency department, clinic, or specialist stroke service) and study population may influence the measured risk. Third, the intensity and timing of secondary preventive treatment may reduce stroke risk after TIA.4, 7, 8 Fourth, the stroke risk after TIA has been shown to vary according to characteristics of the patient (age, blood pressure, diabetes),9, 10 clinical features of the event (focal weakness, speech deficit, and symptom duration),9, 10, 11 and underlying aetiology.12 Thus, differences in study method, setting and population, treatment, and case mix must all be considered when interpreting heterogeneity in measured risk between studies.
We therefore systematically reviewed studies of the risk of stroke within 7 days after a TIA, to estimate stroke risk overall and to determine the influence of study method, setting, population, treatment, and case mix.
Section snippets
Methods
We aimed to identify all studies reporting the risk of stroke within 7 days of TIA, irrespective of the study design, setting, or language, in accordance with the MOOSE guidelines13 for meta-analysis of observational studies in epidemiology. Ovid Medline (1950 to June, 2007) and Embase (1980 to June, 2007) were searched by use of both the medical subject heading (MESH) terms and text words: [TIA OR amaurosis fugax OR transient isch(a)emic attack] AND [outcome OR prognosis OR follow-up OR cohort
Results
The search of electronic databases yielded 11 350 publications. After initial screening, 69 reports were identified for full-text review. 15 additional reports were identified by searching relevant reference lists and abstract books from recent conferences. No further studies were identified by hand searches of the three journals from which most eligible studies were identified electronically (Stroke, The Lancet, and Cerebrovascular Diseases). Of the resulting 84 reports that were reviewed in
Discussion
This review showed an overall risk of stroke at 2 days after TIA of 3·1% (95% CI 2·0–4·1) in 15 cohorts including 9433 patients, and 5·2% (3·9–6·5) at 7 days in 17 cohorts including 7830 subjects, but with significant heterogeneity (p<0·0001) between studies for both results. This degree of heterogeneity, the high correlation between stroke risks at 0–7 days and 8–90 days in individual studies, and the reduction in heterogeneity by stratification of studies by common methods and setting suggest
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