Variations between countries in outcome after stroke in the International Stroke Trial (IST)

Background and Purpose-This study describes the large variations in outcome after stroke between countries that participated in the International Stro ke Trial and seeks to define whether they could be explained by variations in case mix or by other factors. Methods-We analyzed data from the 15 116 patients recruited in Argentina, A ustralia, Italy, the Netherlands, Norway, Poland, Sweden, Switzerland, and the United Kingdom, We compared crude case fatality and the proportion of p atients dead or dependent at 6 months; we used logistic regression to adjus t for age, sex, atrial fibrillation, systolic blood pressure, level of cons ciousness, and number of neurological deficits, We used the frequency of pr erandomization head CT scan and prescription of aspirin at discharge to ind icate quality of care, Results-The differences in outcome (all treatment groups combined) between the "best" and "worst" countries were very large for death (171 cases per 1 000 patients) and for death or dependency (375 cases per 1000 patients). Th e differences were somewhat smaller after adjustment for case mix (160 and 311 cases per 1000 patients, respectively), Process of care may have accoun ted for some but not all of the residual variation in outcome. Conclusions-Adjustment for case mix explained only some of the variation in outcome between countries. The residual differences in outcome were too la rge to be explained by variations in care and most likely reflect differenc es in unmeasured baseline factors. These findings demonstrate the need to a chieve balance of treatment and control within each country in multinationa l randomized controlled stroke trials and the need for caution in the inter pretation of nonrandomized comparisons of outcome after stroke between coun tries.