Transient Ischaemic Attack – Obtaining a Differential Diagnosis and Predicting Patient Risk
condition with a low subsequent risk of stroke (approximately 1–2% at one week and 2–4% at one month) and other vascular events.19 However, recent research using more reliable methodology based on prospective data and recruiting patients in the acute phase has shown that these were underestimates, and the risk of stroke is particularly high in the first few hours and days after TIA, with estimates as high as 10–15% at one week in some studies.20
This high early risk following TIA poses a dilemma to clinicians and healthcare services because, although the majority of patients will suffer transient symptoms only with no acute sequelae, an important minority will go on to suffer a potentially disabling stroke that could be preventable with appropriate treatment. Prognostic scores have therefore been developed as a means of identifying high- (and low-) risk individuals and thereby aiding effective triage from emergency departments and primary care to specialist services, as well as informing public education and targeting secondary prevention treatment.
Methods of Risk Prediction Clinical Features – The ABCD System
These included age >60 years, symptom duration >10 minutes, motor weakness, speech impairment and diabetes. These and other factors identified as being associated with early stroke risk in two other studies22,23
stroke risk within seven days after TIA.24 in three further cohorts of TIA patients.
Five factors were found to be independently associated with high risk of stroke at three months in an emergency department cohort of TIA patients.21
were used to derive the ABCD score to predict The score was then validated
The ABCD score is based on four clinical features and is out of a total of six (see Table 3). It was found to be highly predictive of stroke at seven days after TIA with area under the receiver operator curve (ROC) statistics of 0.85 (0.78–0.91), 0.91 (0.86–0.95) and 0.80 (0.72–0.89) for each of the validation cohorts (see Figure 1). Almost all strokes occurred among patients scoring over 3, with the rates of stroke rising steeply with increasing score above 4.
Although diabetes was found to be predictive of early stroke in the ABCD score, it was not included. However, the ABCD scoring system was further validated in cohorts of patients recruited in California, US, and refined with the subsequent addition of one point for diabetes to make the ABCD2 score out of seven (see Table 3 and Figure 2).25
The ABCD system was developed for use by primary care and emergency care physicians prior to specialist evaluation and is based on clinical information that is readily available following a brief patient assessment. However, prediction scores in general require validation by independent users to demonstrate generalisability prior to their wider use in clinical practice.26
In terms of its clinical and statistical performance, both the ABCD and ABCD2 scores have been further validated in independent cohorts since publication in 2005 and 2007, respectively. In a systematic review, 20 cohorts were identified reporting the performance of the ABCD and ABCD2 scores in 9,808 subjects with 456 strokes at seven days.27
Pooled estimates of the area under the
curve (AUC) for the ABCD and ABCD2 scores were 0.72 (0.67–0.77) and 0.72 (0.63–0.80), respectively, for seven-day stroke risk.
EUROPEAN NEUROLOGICAL REVIEW
Figure 2: Observed Stroke Risk at Two, Seven, 30 and 90 Days After Transient Ischaemic Attack Stratified by ABCD2 Score Pooled from Six Validation Cohorts
25
20
15
10
5
0 01 2 2-day risk Source: Johnston et al., 2007.25
Figure 3: Diffusion-weighted Magnetic Resonance Images
3 7-day risk 45 6 ABCD² score 30-day risk 90-day risk 7
Left: Patient with right striato-capsular ischaemic stroke and a recent transient ischaemic attack. Right: patient with right carotid stenosis showing multiple recent areas of ischaemia in the right carotid territory.
Predictive power was greater in two additional cohorts that included patients with both suspected and confirmed TIA compared with cohorts of confirmed TIA patients only. These findings suggest that the ABCD system works both diagnostically, detecting ‘true’ TIA patients with a vascular cause, and prognostically, identifying those ‘true’ TIA patients at highest risk.
Both the usefulness and performance of the ABCD2 score have led to its widespread use in clinical practice and incorporation into guidelines.28,29
Vascular Territory
The early risk of stroke after TIA also depends on the vascular territory of the event. Monocular events (amaurosis fugax) have consistently been found to be associated with a lower risk of stroke in comparison with cerebral events.30
47
Stroke risk (%)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116