ABCD2 Score for TIA

Addition of the selected points.

• In one study of 713 patients reviewed by an expert neurologist, 642 (90%) were judged to likely have experienced a true TIA. (Josephson 2008)
  • Ninety-day stroke risk was 24% (95% CI, 20% to 27%) in the group judged to have experienced a true TIA and 1.4% (0% to 7.6%) in the group judged to not have a true TIA (P<0.0001). (Josephson 2008)
  • ABCD² scores were higher in those judged to have a true TIA compared with others (P=0.0001). In the group judged to have a true TIA, 90-day stroke risk increased as ABCD² score increased (P<0.0001). (Josephson 2008)
• In its derivation study, the ABCD² score classified 21% of patients as high risk (score 6-7, 8.1% 2-day stroke risk), 45% as moderate risk (score 4-5, 4.1% 2-day stroke risk), and 34% as low risk (score 0-3, 1.0% 2-day stroke risk). (Johnston 2007)
• The largest ED-based study was a prospective cohort study of 2,056 subjects and found that the ABCD² score performed poorly in the acute setting. (Perry 2011)
  • In high risk patients (score >5) the ABCD² score was only 31.6% sensitive identifying patients who suffered a stroke within 7 days. (Perry 2011)
  • Using the low risk cut-off recommended by AHA (score >2) the ABCD² score had a specificity of only 12.5% for stroke within 7 days. (Perry 2011)
  • This study found the the ABCD² score was incorrectly calculated in the ED in 1/3 of patients. (Perry 2011)
• A meta-analysis of 33 studies including 16,070 subjects found that the ABCD² score performed poorly in patients with high baseline stroke risk, and was only marginally better when applied to low risk patients. (Sanders 2012)
  • Positive likelihood ratios ranged from 1-2. (Sanders 2012)
  • Negative likelihood ratios ranged from 0.4-1. (Sanders 2012)
  • The authors conclude that the ABCD² score would require further evaluation and validation before “confidently recommending the tool in guidelines.” (Sanders 2012)
• A review of this meta-analysis noted that the majority of the included studies were retrospective and that only 8 of the 33 included patients presenting to the ED (this subgroup was not separately analysed). (Lee 2013)
• The authors note that the poor performance of the ABCD² score in the ED setting, combined with difficulties in arranging the necessary imaging and specialty follow-up within the AHA recommended 24-hour window, that most ED physicians were likely to choose to perform a rapid evaluation of TIA patients (imaging, possible neurology consultation) regardless of the ABCD2 score. (Lee 2013)
• A prospective observational study of 637 patients presenting to the ED found that the ABCD² score did not add incremental value beyond an ED evaluation that included central nervous system and carotid artery imaging in the ability to risk-stratify patients with transient ischemic attack in the study's cohort. (Stead 2010)
  • In this population of patients with TIA patients, a rapid ED-based outpatient protocol that included early carotid imaging and treatment when appropriate, found that the rate of stroke was independent of ABCD² risk stratification. (Stead 2010)

See formula table, below:

There are approximately 250,000 transient ischemic attacks (TIAs) diagnosed in the United States annually.

The ABCD² score may help physicians identify those patients with TIA who are at very low risk of stroke and may be appropriate for an outpatient work-up vs. those who are at increased risk and may benefit from hospital admission.

The ABCD² score can help physicians risk stratify stroke in patients presenting with a TIA.

The ABCD² score was developed to help physicians risk stratify patients presenting with a TIA for how likely they are to suffer a subsequent stroke.

• The largest prospective study of using the ABCD² score in the emergency department found that the score performed poorly (low sensitivity for identifying low risk patients, low specificity for identifying high risk patients).
• Multiple studies have shown that as the ABCD² score increases the risk of a subsequent stroke also increases.
• Patients with a low baseline risk of stroke (≤ 2%) with a low ABCD² score (0-2) are at low risk for having a stroke within the next 7 days (0.4-0.8%).

Points to keep in mind:

• The ABCD² score was developed in the outpatient (non-emergency department) setting.
• It has been shown to have lower accuracy when used by non-specialists (primary care or emergency physicians).
• The ABCD² has less impact on risk stratification when applied in settings where the patients were at low baseline risk of stroke.

• The ABCD² score should not be used as a substitute for clinical judgement or decision making.
• In populations with a low baseline stroke risk, a low ABCD² score (0-2) correlates with a less than 1% risk of stroke within the next week. These patients may be appropriate for expedited outpatient evaluation.
• In centers where computed tomography and carotid ultrasound studies are performed in collaboration with a stroke service, adding the ABCD² score to the evaluation appears unnecessary.

Consider further imaging modalities including MRI and carotid ultrasound.

Consider consulting Neurology to help determine whether the patient would benefit from further inpatient evaluation or to expedite outpatient follow-up when appropriate.

In patients who are determined at high risk for developing a stroke:

• Consult Neurology.
• Consider obtaining an MRI and other appropriate vascular and embolic imaging.
• Have a lower threshold to admit to the patient for further evaluation.

In patients who are determined to be at low risk of developing a stroke in the short term:

• Arrange expedited evaluation as an outpatient with the goal of obtaining the relevant studies and consultations within 24 hours.