Fast track — ArticlesA simple score (ABCD) to identify individuals at high early risk of stroke after transient ischaemic attack
Introduction
Ischaemic strokes are frequently preceded by a transient ischaemic attack (TIA).1 However, because of methodological problems in early studies of prognosis, the immediate risk of stroke after a TIA was underestimated for many years.2, 3 Hospital-based and population-based cohort studies have reported 7-day risks of stroke of up to 10%.4, 5, 6, 7, 8 However, there is substantial international variation in how patients with suspected TIA are managed in the acute phase, with some health-care systems providing immediate emergency inpatient care and others providing non-emergency outpatient clinic assessment,9, 10 and there is little consensus about which strategy is most cost-effective.11, 12 North American and UK guidelines simply state that all patients in whom a diagnosis of TIA is suspected should be assessed and investigated within 7 days,13, 14 although this aim is frequently not achieved in practice. However, the key question is not, in fact, whether emergency inpatient care or non-emergency outpatient care is most appropriate. Rather, it is: for which patients is emergency assessment needed, and which patients can be appropriately managed in a non-emergency outpatient setting? Only about 50% of patients referred for specialist assessment with suspected TIA have the diagnosis confirmed, and so even if the 7-day stroke risk after a TIA is as high as 10%, 95% of referrals will not have a stroke in that period.
Validated models are available for long-term risk of stroke after TIA or minor stroke,15, 16, 17 and there are some unvalidated reports of predictors of stroke at 3 months or 1 year after a TIA,4, 7, 8 but the practical clinical requirement is for prediction of stroke during the first few days after the event, for which there are currently no published models. We therefore aimed to derive and validate a simple risk score to predict stroke during the first 7 days after a TIA with three potential uses in mind: to allow primary-care doctors and other front-line physicians to identify which of the patients in whom they suspect a diagnosis of TIA should be referred-on for assessment as an emergency; to allow secondary-care physicians to determine which patients with probable or definite TIA need emergency investigation and treatment; and to allow public education about the need for medical attention after a TIA to focus on the specific symptoms and characteristics that identify high-risk individuals.
Section snippets
Derivation of a simple risk score
We derived the score in the population-based cohort of TIA patients in the Oxfordshire Community Stroke Project (OCSP). The methods of the OCSP have been reported elsewhere.18, 19 Briefly, a population of about 105 000 registered with 50 family doctors in ten practices in Oxfordshire, UK, was studied. All patients with a possible diagnosis of TIA during the study period (1981–86) were reported to a study neurologist and assessed as soon as possible after the event. The characteristics of the
Results
Table 1 shows the baseline characteristics of the OCSP and OXVASC cohorts of patients with probable or definite TIA. Data were missing on duration of TIA in four patients in OCSP, three of whom also had missing data on clinical features, leaving 205 of 209 (98%) patients with complete data (table 1). Complete data were available for 188 of 190 (99%) OXVASC patients. The OXVASC cohort was older than the OCSP cohort (p=0·002), had a higher proportion of women (p=0·02), higher rates of previously
Discussion
We have derived and validated a simple score to predict stroke in the 7 days after a TIA, based on age, blood pressure, clinical features, and duration of symptoms. We used data from three rigorous clinical studies. OXVASC and OCSP are two of only a very few prospective, truly population-based studies of TIA with high levels of ascertainment and detailed assessment by neurologists. The hospital-referred clinic series was also valuable in that, unlike other such studies, all referrals were
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