Predicting Clinical Outcomes After Thrombolysis Using the iScore

BACKGROUND AND PURPOSE: The ischemic stroke risk score (iScore) is a validated tool developed to estimate the risk of death and functional outcomes early after an acute ischemic stroke. Our goal was to determine the ability of the iScore to estimate clinical outcomes after intravenous thrombolysis tissue-type plasminogen activator (tPA) in the Virtual International Stroke Trials Archive (VISTA). METHODS: We applied the iScore (www.sorcan.ca/iscore) to patients with an acute ischemic stroke within the VISTA collaboration to examine the effect of tPA. We explored the association between the iScore (<200 and ≥200) and the primary outcome of favorable outcome at 3 months defined as a modified Rankin scale score of 0 to 2. Secondary outcomes included death at 3 months, catastrophic outcomes (modified Rankin scale, 4-6), and Barthel index >90 at 3 months. RESULTS: Among 7140 patients with an acute ischemic stroke, 2732 (38.5%) received tPA and 711 (10%) had an iScore ≥200. Overall, tPA treatment was associated with a significant improvement in the primary outcome among patients with an iScore <200 (38.9% non-tPA versus 47.5% tPA; P<0.001) but was not associated with a favorable outcome among patients with an iScore ≥200 (5.5% non-tPA versus 7.6% tPA; P=0.45). In the multivariable analysis after adjusting for age, baseline National Institutes of Health Stroke Scale, and onset-to-treatment time, there was a significant interaction between tPA administration and iScore; tPA administration was associated with 47% higher odds of a favorable outcome at 3 months among patients with an iScore <200 (odds ratio, 1.47; 95% confidence interval, 1.30-1.67), whereas the association between tPA and favorable outcome among those with an iScore ≥200 remained nonsignificant (odds ratio, 0.80; 95% confidence interval, 0.45-1.42). A similar pattern of benefit with tPA among patients with an iScore <200, but not ≥200, was observed for secondary outcomes including death. CONCLUSIONS: The iScore is a useful and validated tool that helps clinicians estimate stroke outcomes. In stroke patients participating in VISTA, an iScore <200 was associated with better outcomes at 3 months after tPA.