In this post, I link to and excerpt from Prospective validation of Canadian TIA Score and comparison with ABCD2 and ABCD2i for subsequent stroke risk after transient ischaemic attack: multicentre prospective cohort study [PubMed Abstract] [Full-Text HTML]. BMJ. 2021; 372: n49.
Published online 2021 Feb 4. doi: 10.1136/bmj.n49
What follows is from the above resource.
What is already known on this topic
Patients with transient ischaemic attack are at heightened risk for a subsequent major stroke or death, especially within the first few days
Optimising stroke prevention requires more precise risk stratification than existing tools can offer, to minimise both under-treatment and over-treatment
What this study adds
After transient ischaemic attack, the Canadian TIA Score outperformed other tools to stratify seven day risk of stroke, with or without carotid interventions
Incorporating this now validated core into management plans at the index emergency visit should improve early decision making on hospital admission, timing of investigations, and specialist referral
Objective: To validate the previously derived Canadian TIA Score to stratify subsequent stroke risk in a new cohort of emergency department patients with transient ischaemic attack.
Design: Prospective cohort study.
Setting: 13 Canadian emergency departments over five years.
Participants: 7607 consecutively enrolled adult patients attending the emergency department with transient ischaemic attack or minor stroke.
Main outcome measures: The primary outcome was subsequent stroke or carotid endarterectomy/carotid artery stenting within seven days. The secondary outcome was subsequent stroke within seven days (with or without carotid endarterectomy/carotid artery stenting). Telephone follow-up used the validated Questionnaire for Verifying Stroke Free Status at seven and 90 days. All outcomes were adjudicated by panels of three stroke experts, blinded to the index emergency department visit.
Results: Of the 7607 patients, 108 (1.4%) had a subsequent stroke within seven days, 83 (1.1%) had carotid endarterectomy/carotid artery stenting within seven days, and nine had both. The Canadian TIA Score stratified the risk of stroke, carotid endarterectomy/carotid artery stenting, or both within seven days as low (risk ≤0.5%; interval likelihood ratio 0.20, 95% confidence interval 0.09 to 0.44), medium (risk 2.3%; interval likelihood ratio 0.94, 0.85 to 1.04), and high (risk 5.9% interval likelihood ratio 2.56, 2.02 to 3.25) more accurately (area under the curve 0.70, 95% confidence interval 0.66 to 0.73) than did the ABCD2 (0.60, 0.55 to 0.64) or ABCD2i (0.64, 0.59 to 0.68). Results were similar for subsequent stroke regardless of carotid endarterectomy/carotid artery stenting within seven days.
Conclusion: The Canadian TIA Score stratifies patients’ seven day risk for stroke, with or without carotid endarterectomy/carotid artery stenting, and is now ready for clinical use. Incorporating this validated risk estimate into management plans should improve early decision making at the index emergency visit regarding benefits of hospital admission, timing of investigations, and prioritisation of specialist referral.
Our study validates the predictive performance of the Canadian TIA Score in a broad sample of patients prospectively enrolled in the emergency department with a diagnosis of transient ischaemic attack or minor stroke. To improve the generalisability of the score, we included both community and academic centres, including six new sites that were not involved in the derivation study. The score was able to correctly stratify many more patients into pre-specified risk zones than were other scores based on the ABCD paradigm. Having withstood prospective validation in a newly assembled, contemporaneous cohort, and satisfying stringent criteria for the development of a clinical decision rule/score, this tool can now be adopted into clinical practice.
The Canadian TIA Score performed significantly better than the ABCD2 scores. . . . Although our score is more complex and is not intended to be memorised, it requires only routinely available information from the history, bedside assessment, and test results to stratify patients. It can be readily used and applied by physicians in the emergency department, as it does not require advanced neuroimaging, which is often unavailable. It allows one to customise the urgency of, for example, advanced neuroimaging or to inform the decision surrounding inpatient admission versus outpatient specialty consultation according to local preferences or to incorporate patients’ preferences. Many hospitals are unable to offer 24/7 access to magnetic resonance imaging and/or need to transfer patients for specialty consultation. Stratifying the risk for patients allows for more standardised care, more equitable deployment of constrained resources, and probably better outcomes.29 30
Comparisons with other studies
The definition of transient ischaemic attack continues to evolve and requires absence of infarction on magnetic resonance imaging.31 Although this definition provides greater diagnostic accuracy and excludes many non-ischaemic aetiologies that mimic transient ischaemic attack or stroke than the World Health Organization’s time based definition, it is not practical in emergency departments in much of the US, most of Canada, and most of the world, given the requirement for immediate magnetic resonance imaging. Hence, our work has emphasised a working emergency department diagnosis of transient ischaemic attack or minor stroke as the target population for the Canadian TIA Score.9 Conversely, an abnormal magnetic resonance imaging scan alone confers only a modest increase in subsequent risk of stroke, as shown in a recent study of patients diagnosed as having a possible transient ischaemic attack or minor stroke: very few had a subsequent stroke at one year despite 13.5% having abnormalities on imaging. Patients high risk features with or without positive diffusion weighted magnetic resonance imaging scans had a combined subsequent stroke rate of 0.7%.32 Five high risk features were identified for the composite outcome of subsequent stroke, subsequent transient ischaemic attack, death, or myocardial infarction, but the authors concluded that they were not sensitive enough in identifying patients with subsequent events to be used clinically.
The Canadian TIA Score includes 13 variables, so clinicians will probably need to use an online calculator or smartphone application to calculate the risk of their patients. Given that physicians already use these tools for many patients, this is likely a minor limitation and represents the heterogeneity of risk assessment for cerebral ischaemia.
The Canadian TIA score was able to risk stratify patients into the three risk groups efficiently (table 3), with about one in six patients found to be at low risk (<1% risk for the primary outcome; interval likelihood ratio 0.20, 95% confidence interval 0.09 to 0.44), and one in eight at high risk (>5% risk; interval likelihood ratio 2.56, 2.02 to 3.25). The remainder were at medium risk, with a subsequent seven day event rate of 2.3% and an interval likelihood ratio of 0.94 (0.85 to 1.04). These risk strata were similar for the secondary outcome of subsequent stroke (table 4) and for risk stratification at both two and 90 days (appendix 2).
Clinicians may now use the Canadian TIA Score to stratify patients as being at low, medium, or high risk for subsequent early stroke (with or without early carotid revascularisation). The optimal management pathway at the local or regional level can be determined on the basis of the expected risk at a given risk category (for example, same day computed tomography with routine follow-up for patients at low risk, computed tomography angiography and rapid follow-up for those at medium risk, and neurology consultation in the emergency department for those at high risk).
The Canadian TIA Score identifies the risk of patients with transient ischaemic attack for subsequent stroke or carotid artery revascularisation within seven days. Incorporating this validated risk estimate into management plans should improve decisions on the benefits of hospital admission at the index visit, urgency of testing and interventions, and prioritisation of specialist follow-up for patients discharged from the emergency department.