Performance of the ABCD2 score for stroke risk post TIA: meta-analysis and probability modeling.

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.