Leukocytosis in acute stroke: Relation to initial stroke severity, infarct size, and outcome: The copenhagen stroke study

Leukocytosis is a common finding in the acute phase of stroke. A detrimental effect of leukocytosis on stroke outcome has been suggested, and trials aiming at reducing the leukocyte response in acute stroke are currently being conducted. However, the influence of leukocytosis on stroke outcome has not been clarified. Methods: In 763 unselected patients with stroke admitted within 24 hours from onset, we prospectively studied the relation between leukocyte count and outcome considering relevant confounders and predictors such as initial stroke severity, risk factor profile, body temperature, and infection. Results: Univariate, leukocyte count on admission was significantly related to initial stroke severity (assessed by the Scandinavian Stroke Scale), lesion size on computed tomography, mortality, and outcome in survivors. However, multivariate regression analysis revealed that only the relation between leukocytosis and initial stroke severity was independent of other factors, whereas the relations found univariately between leukocytosis and lesion size, mortality, and outcome in survivors disappeared when initial stroke severity was included in the multivariate model. Conclusion: Leukocytosis on admission was related to initial stroke severity but not to outcome. Leukocyte count on admission seems merely to reflect initial stroke severity and is most likely a stress response with no independent influence on outcome. Our study may suggest that attempts aimed merely at lowering leukocyte count in peripheral circulating blood in the acute phase of stroke cannot be expected to improve outcome.