Influence of racial differences on outcomes after thrombolytic therapy in acute ischemic stroke

Background: The National Institutes of Neurological Disorders and Stroke and the European Co-operative Acute Stroke III trials enrolled a largely Caucasian population, but the results are often extrapolated onto non-Caucasians. A limited number of nonrandomized studies have proposed that non-Caucasian patients show differential response to tissue plasminogen activator.

Aims and/or hypothesis: We examined if non-Caucasian patients of mixed national origin within the Virtual International Stroke Trials Archives neuroprotection trials responded differently to tissue plasminogen activator compared with Caucasians.

Methods: We matched patients within each race-subtype for age, baseline National Institutes of Health Stroke Scales, and diabetes status, and excluded outliers. We tested for an interaction of race ethnicity with tissue plasminogen activator on predicting outcomes at α = 0·05. We compared 90-day ordinal outcome (modified Rankin Scale; primary analysis) and dichotomized outcomes (modified Rankin Scale 0-1; modified Rankin Scale 0-2; survival) within individual race ethnicity.

Results: One thousand nine hundred forty-six thrombolysed patients (125 Blacks, 39 Asians, and 1821 Caucasians) were matched with 1946 non-thrombolysed patients in each race ethnicity group. Postmatching, there were no imbalances in baseline National Institutes of Health Stroke Scales and age between the groups (P > 0·05). The interaction of tissue plasminogen activator with race ethnicity was nonsignificant in ordinal (P = 0·4) and in dichotomized outcome models (P > 0·05). Ordinal odds for improved outcomes were 1·5 for all patients (P < 0·05). Ordinal odds for Caucasians were 1·5 (P < 0·05); for Blacks, 2·1 (P < 0·05); and for Asians, 1·2 (P > 0·05; 1·6 after 1:2 matching with nonthrombolysed, because of small numbers). Dichotomized functional outcomes improved after thrombolysis overall, in Caucasians, in Blacks (modified Rankin Scale 0-2 only), and in Asians (after 1:2 matching; P > 0·05). Odds for survival were consistent across all groups.

Conclusions: These results do not suggest a differential response to tissue plasminogen activator based on race ethnicity. Among Asians, data were particularly sparse, and results should be interpreted with caution.