Objective: To study the accuracy of the ABCD2 score in predicting early stroke risk following TIA and to model post-test probability of stroke for varying cutoff scores and baseline stroke risk.
Methods: Medline, PubMed, Embase, conference proceedings, and manuscript references up to October 2010 were searched for studies reporting ABCD2 score and stroke outcome after TIA. Additional data were requested from authors. Meta-analysis, meta-regression, and post-test probability modeling were undertaken to assess prediction of stroke at 2, 7, and 90 days.
Results: Of 44 eligible studies, data were available for 33 (16,070 patients): 26/33 reported stroke at 2 days (533 strokes), 32/33 at 7 days (781 strokes), and 28/33 at 90 days (1,028 strokes) after TIA. Using scores 0-3 ("low risk") and 4-7 ("high risk") for stroke at 7 days, pooled measures were sensitivity 0.89 (0.87-0.91), specificity 0.34 (0.33-0.35), positive predictive value 0.08 (0.07-0.09), negative predictive value 0.98 (0.98-0.98), positive likelihood ratio (PLR) 1.43 (1.33-1.54), negative likelihood ratio (NLR) 0.40 (0.33-0.50), and area under the curve (AUC) 0.70 (0.62-0.78). Results were similar at days 2 and 90. There was moderate heterogeneity while pooling PLR (p < 0.01, I(2) >50%), with stroke specialist TIA diagnosis associated with slightly higher PLR. At 5% baseline stroke risk, ABCD2 >3 indicated an absolute increase in 7-day stroke risk of only 2.0% while a score ≤3 indicated a 2.9% decrease in risk. Changes in risk were very small when baseline stroke risk was lower.
Conclusions: The ABCD2 score leads to only small revisions of baseline stroke risk particularly in settings of very low baseline risk and when used by nonspecialists.