A simple score (ABCD) to identify individuals at high early risk of stroke after transient ischaemic attack.

BACKGROUND: Effective early management of patients with transient ischaemic attacks (TIA) is undermined by an inability to predict who is at highest early risk of stroke. METHODS: We derived a score for 7-day risk of stroke in a population-based cohort of patients (n=209) with a probable or definite TIA (Oxfordshire Community Stroke Project; OCSP), and validated the score in a similar population-based cohort (Oxford Vascular Study; OXVASC, n=190). We assessed likely clinical usefulness to front-line health services by using the score to stratify all patients with suspected TIA referred to OXVASC (n=378, outcome: 7-day risk of stroke) and to a hospital-based weekly TIA clinic (n=210; outcome: risk of stroke before appointment). RESULTS: A six-point score derived in the OCSP (age [> or =60 years=1], blood pressure [systolic >140 mm Hg and/or diastolic > or =90 mm Hg=1], clinical features [unilateral weakness=2, speech disturbance without weakness=1, other=0], and duration of symptoms in min [> or =60=2, 10-59=1, <10=0]; ABCD) was highly predictive of 7-day risk of stroke in OXVASC patients with probable or definite TIA (p<0.0001), in the OXVASC population-based cohort of all referrals with suspected TIA (p<0.0001), and in the hospital-based weekly TIA clinic-referred cohort (p=0.006). In the OXVASC suspected TIA cohort, 19 of 20 (95%) strokes occurred in 101 (27%) patients with a score of 5 or greater: 7-day risk was 0.4% (95% CI 0-1.1) in 274 (73%) patients with a score less than 5, 12.1% (4.2-20.0) in 66 (18%) with a score of 5, and 31.4% (16.0-46.8) in 35 (9%) with a score of 6. In the hospital-referred clinic cohort, 14 (7.5%) patients had a stroke before their scheduled appointment, all with a score of 4 or greater. CONCLUSIONS: Risk of stroke during the 7 days after TIA seems to be highly predictable. Although further validations and refinements are needed, the ABCD score can be used in routine clinical practice to identify high-risk individuals who need emergency investigation and treatment.

Population-based study of event-rate, incidence, case fatality, and mortality for all acute vascular events in all arterial territories (Oxford Vascular Study).

BACKGROUND: Acute coronary, cerebrovascular, and peripheral vascular events have common underlying arterial pathology, risk factors, and preventive treatments, but they are rarely studied concurrently. In the Oxford Vascular Study, we determined the comparative epidemiology of different acute vascular syndromes, their current burdens, and the potential effect of the ageing population on future rates. METHODS: We prospectively assessed all individuals presenting with an acute vascular event of any type in any arterial territory irrespective of age in a population of 91 106 in Oxfordshire, UK, in 2002-05. FINDINGS: 2024 acute vascular events occurred in 1657 individuals: 918 (45%) cerebrovascular (618 stroke, 300 transient ischaemic attacks [TIA]); 856 (42%) coronary vascular (159 ST-elevation myocardial infarction, 316 non-ST-elevation myocardial infarction, 218 unstable angina, 163 sudden cardiac death); 188 (9%) peripheral vascular (43 aortic, 53 embolic visceral or limb ischaemia, 92 critical limb ischaemia); and 62 unclassifiable deaths. Relative incidence of cerebrovascular events compared with coronary events was 1.19 (95% CI 1.06-1.33) overall; 1.40 (1.23-1.59) for non-fatal events; and 1.21 (1.04-1.41) if TIA and unstable angina were further excluded. Event and incidence rates rose steeply with age in all arterial territories, with 735 (80%) cerebrovascular, 623 (73%) coronary, and 147 (78%) peripheral vascular events in 12 886 (14%) individuals aged 65 years or older; and 503 (54%), 402 (47%), and 105 (56%), respectively, in the 5919 (6%) aged 75 years or older. Although case-fatality rates increased with age, 736 (47%) of 1561 non-fatal events occurred at age 75 years or older. INTERPRETATION: The high rates of acute vascular events outside the coronary arterial territory and the steep rise in event rates with age in all territories have implications for prevention strategies, clinical trial design, and the targeting of funds for service provision and research.

Change in stroke incidence, mortality, case-fatality, severity, and risk factors in Oxfordshire, UK from 1981 to 2004 (Oxford Vascular Study).

BACKGROUND: The incidence of stroke is predicted to rise because of the rapidly ageing population. However, over the past two decades, findings of randomised trials have identified several interventions that are effective in prevention of stroke. Reliable data on time-trends in stroke incidence, major risk factors, and use of preventive treatments in an ageing population are required to ascertain whether implementation of preventive strategies can offset the predicted rise in stroke incidence. We aimed to obtain these data. METHODS: We ascertained changes in incidence of transient ischaemic attack and stroke, risk factors, and premorbid use of preventive treatments from 1981-84 (Oxford Community Stroke Project; OCSP) to 2002-04 (Oxford Vascular Study; OXVASC). FINDINGS: Of 476 patients with transient ischaemic attacks or strokes in OXVASC, 262 strokes and 93 transient ischaemic attacks were incident events. Despite more complete case-ascertainment than in OCSP, age-adjusted and sex-adjusted incidence of first-ever stroke fell by 29% (relative incidence 0.71, 95% CI 0.61-0.83, p=0.0002). Incidence declined by more than 50% for primary intracerebral haemorrhage (0.47, 0.27-0.83, p=0.01) but was unchanged for subarachnoid haemorrhage (0.83, 0.44-1.57, p=0.57). Thus, although 28% more incident strokes (366 vs 286) were expected in OXVASC due to demographic change alone (33% increase in those aged 75 or older), the observed number fell (262 vs 286). Major reductions were recorded in mortality rates for incident stroke (0.63, 0.44-0.90, p=0.02) and in incidence of disabling or fatal stroke (0.60, 0.50-0.73, p<0.0001), but no change was seen in case-fatality due to incident stroke (17.2% vs 17.8%; age and sex adjusted relative risk 0.85, 95% CI 0.57-1.28, p=0.45). Comparison of premorbid risk factors revealed substantial reductions in the proportion of smokers, mean total cholesterol, and mean systolic and diastolic blood pressures and major increases in premorbid treatment with antiplatelet, lipid-lowering, and blood pressure lowering drugs (all p<0.0001). INTERPRETATION: The age-specific incidence of major stroke in Oxfordshire has fallen by 40% over the past 20 years in association with increased use of preventive treatments and major reductions in premorbid risk factors.

Direct assessment of completeness of ascertainment in a stroke incidence study.

BACKGROUND AND PURPOSE: Validity of comparisons of stroke incidence between studies or time periods depends on the completeness of ascertainment. Ascertainment cannot be reliably assessed indirectly by statistical methods, such as capture-recapture. We report the first use of direct methods to determine the completeness of different ascertainment strategies in a population-based stroke incidence study (Oxford Vascular Study). METHODS: We assessed completeness of 2 different ascertainment strategies: the core methods common to most previous incidence studies and core plus supplementary methods used in some studies (including access to carotid and brain imaging referrals and assessment of patients referred as "transient ischemic attack" or "recurrent stroke"). We assessed completeness of ascertainment in 2 ways. First, we searched anonymized primary care electronic patient records of the whole study population (n=90,542). Second, we interviewed and followed-up a high-risk subset of our study population: all patients who had an acute coronary or peripheral vascular event or a related elective investigation or intervention. RESULTS: 126 strokes were ascertained by the core plus supplementary methods, of which only 108 were identified by the core methods alone. Only 2 additional incident strokes were identified by access to primary care electronic patient records of the whole study population. Assessment and follow-up of 1103 high-risk individuals (5.5% of our total study population aged older than 60 years) identified 16 incident strokes. However, all 16 had already been ascertained by the core plus supplementary methods. CONCLUSIONS: The core methods of ascertainment used in some stroke incidence studies lead to significant underascertainment. However, direct assessment of ascertainment suggests that the supplementary methods used in recent studies can lead to near-complete ascertainment.

Early stroke risk and ABCD2 score performance in tissue- vs time-defined TIA: a multicenter study.

OBJECTIVES: Stroke risk immediately after TIA defined by time-based criteria is high, and prognostic scores (ABCD2 and ABCD3-I) have been developed to assist management. The American Stroke Association has proposed changing the criteria for the distinction between TIA and stroke from time-based to tissue-based. Research using these definitions is lacking. In a multicenter observational cohort study, we have investigated prognosis and performance of the ABCD2 score in TIA, subcategorized as tissue-positive or tissue-negative on diffusion-weighted imaging (DWI) or CT imaging according to the newly proposed criteria. METHODS: Twelve centers provided data on ABCD2 scores, DWI or CT brain imaging, and follow-up in cohorts of patients with TIA diagnosed by time-based criteria. Stroke rates at 7 and 90 days were studied in relation to tissue-positive or tissue-negative subcategorization, according to the presence or absence of brain infarction. The predictive power of the ABCD2 score was determined using area under receiver operator characteristic curve (AUC) analyses. RESULTS: A total of 4,574 patients were included. Among DWI patients (n = 3,206), recurrent stroke rates at 7 days were 7.1%(95% confidence interval 5.5-9.1) after tissue-positive and 0.4% (0.2-0.7) after tissue-negative events (p diff < 0.0001). Corresponding rates in CT-imaged patients were 12.8% (9.3-17.4) and 3.0% (2.0-4.2), respectively (p diff < 0.0001). The ABCD2 score had predictive value in tissue-positive and tissue-negative events (AUC = 0.68 [95% confidence interval 0.63-0.73] and 0.73 [0.67-0.80], respectively; p sig < 0.0001 for both results, p diff = 0.17). Tissue-positive events with low ABCD2 scores and tissue-negative events with high ABCD2 scores had similar stroke risks, especially after a 90-day follow-up. CONCLUSIONS: Our findings support the concept of a tissue-based definition of TIA and stroke, at least on prognostic grounds.