Background:
Much controversy exists as to which TIA patients need to be admitted to the hospital for evaluation and treatment and which can be sent home. One commonly used trigae tool is the ABCD
2
score (Age, presenting Blood Pressure, Clinical symptoms and Duration, and Diabetes). Although this tool gives good information for determining populations at low risk (score of 0-3) and high risk (score of 6-7) of stroke after TIA, it leaves a large moderate risk population (score of 4-5) for whom no clear triage guidance can be given. As previous studies have found large artery atherosclerosis to be a potent risk factor for stroke after TIA, we attempted to further delineate low and high risk TIA populations with the addition of non-invasive arterial imaging to the ABCD
2
score.
Methods:
All patients referred to the Stanford Stroke Service for possible TIA within 72 hrs of symptom onset between July 2007 and February 2010, and all patients referred to the Highland Park Stroke Service for possible TIA within 72 hrs of symptom onset after October 2009 were screened for enrollment in this observational study. Exclusion criteria included age <18 years, use of TPA at initial presentation, and symptoms lasting >24 hours. 352 patients were invited to enroll, 3 refused. Of the 349 enrolled, follow-up was obtained in 346 patients at 30 days. Patients were placed into two groups: 1) those with ABCD
2
scores of 0-3 or scores of 4-5 AND no sign of hemodynamically significant stenosis in an artery within the distribution of the TIA (Low Risk Group); and 2) those with ABCD
2
scores of 6-7 or scores of 4-5 AND a hemodynamically significant stenosis in an artery within the distribution of the TIA (High Risk Group). Non-invasive arterial imaging included CT angiogram, MR angiogram, and carotid ultrasound - all used at the discretion of the treating physician. 30 day stroke rates with 95% confidence intervals were recorded.
Results:
Of the 346 patients enrolled, 295 (85.3%) fell into the "Low Risk Group" based on ABCD
2
scoring and non-invasive arterial imaging. Within that group, the stroke rate at 30 days was 1.0% (3 strokes, 95% CI 0.2-3.1%). Within the "High Risk Group", the stroke rate at 30 days was 5.9% (3 strokes, 95% CI 1.4-16.5%). Within the "Low Risk Group", all 3 of the strokes occurred in patients with ABCD
2
scores of 4-5 (3/133 patients - 2.3% stroke rate with 95% CI 0.5-6.7%). The overall stroke rate was 6/346 (1.7%, 95% CI 0.7-3.8%).
Conclusions:
In our observational study we found that the overall 30 day stroke rate after TIA was quite low. The percentage of all TIA patients falling into the “Low Risk Group” was quite high, and these patients had a particularly low rate of stroke at 30 days. Given the high number of "Low Risk" patients and the low rate of stroke in that group at 30 days, the vast majority of TIA patients could likely be safely evaluated in an rapid outpatient setting provided that the treating physician is confident of the diagnosis.
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