EBQ:Validation and refinement of scores to predict very early stroke risk after transient ischaemic attack

Complete Journal Club Article

Johnston S. et al.. "Validation and refinement of scores to predict very early stroke risk after transient ischaemic attack". Lancet. 2007. 369:(9558):283-9.
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Clinical Question

Aims: To validate two prognostic scores for early risk of stroke after TIA and to derive and validate a unified score optimized for prediction of 2-day stroke risk to inform emergency management

Conclusion

• The ABCD2 score (combining elements of the ABCD and California scores) predicts stroke risk within 2, 7, and 90 days after TIA
• Higher ABCD2 scores correlate with increased short-term stroke risk
• Scores >=4 identify patients at highest risk who warrant urgent evaluation and admission

Major Points

• The ABCD2 score unified two existing prediction tools (ABCD and California) into a single validated instrument
• Score components: Age >=60 (1pt), BP >=140/90 (1pt), Clinical features - unilateral weakness (2pt) or speech impairment without weakness (1pt), Duration >=60min (2pt) or 10-59min (1pt), Diabetes (1pt)
• 2-day stroke risk by score: 0-3 (low) 1.0%, 4-5 (moderate) 4.1%, 6-7 (high) 8.1%
• The score performs better than either predecessor alone for stroke risk stratification
• Widely adopted in emergency medicine for TIA risk stratification and disposition decisions

Study Design

• Retrospective validation study using pooled data from existing cohorts
• Derivation cohort: 1,916 TIA patients from Oxfordshire, UK
• Validation cohorts: 2,893 patients from California and 1,891 from additional UK sites
• Primary Outcome: stroke within 2, 7, and 90 days of TIA

Population

Inclusion Criteria

• Patients diagnosed with TIA by treating physician or neurologist
• Sufficient clinical data to calculate ABCD2 score

Exclusion Criteria

• Patients with stroke rather than TIA at presentation
• Insufficient follow-up data

Interventions

• No therapeutic intervention; this was a predictive score derivation and validation study
• ABCD2 score calculated retrospectively from recorded clinical data
• Stroke outcomes ascertained through chart review and follow-up

Outcomes

Primary Outcome

• Stroke within 2 days by ABCD2 score:
  • Score 0-3: 1.0%
  • Score 4-5: 4.1%
  • Score 6-7: 8.1%

Secondary Outcomes

• 7-day stroke risk: 1.2% (low), 5.9% (moderate), 11.7% (high)
• 90-day stroke risk: 3.1% (low), 9.8% (moderate), 17.8% (high)
• C-statistic for 7-day risk: 0.72 (validation cohort)

Funding

• UK Medical Research Council
• Wellcome Trust