White blood cell count is an independent predictor of outcomes after acute ischaemic stroke

In patients with ischaemic stroke, elevated white blood cell count (WBC) has been associated with stroke severity on admission and poor functional outcome. However, previous studies did not control for confounding factors. We hypothesized that higher WBC is an independent predictor of stroke severity, greater degree of disability and 30-day mortality after acute ischaemic stroke.

Data from the Registry of the Canadian Stroke Network on consecutive patients with acute ischaemic stroke admitted between July 2003 and March 2008 were used. Patients were divided into groups as follows: low WBC (0.1-4 × 10(-9) /l), normal WBC (4.1-10 × 10(-9) /l) and high WBC (10.1-40 × 10(-9) /l). Primary outcome measures were the frequency of moderate/severe strokes on admission (Canadian Neurological Scale ≤ 8), greater degree of disability at discharge (modified Rankin score 3-6) and 30-day mortality. Regression analyses were performed adjusting for confounders.

In total, 8829 patients were included. After adjustment for major potential confounders, every 1 × 10(-9) /l increase in WBC was associated with stroke severity on admission [odds ratio (OR) 1.09; 95%CI 1.07-1.10; P < 0.0001), disability at discharge (OR 1.04; 95%CI 1.02-1.06; P = 0.0005) and 30-day mortality (hazard ratio 1.07; 95%CI 1.05-1.08; P < 0.0001). The Kaplan-Meier curves indicate that elevated WBC is associated with higher mortality after acute ischaemic stroke (P = 0.001).

In patients with acute ischaemic stroke, higher WBC on admission is an independent predictor of stroke severity on admission, greater degree of disability at discharge and 30-day mortality. These results reinforce the need for further studies focused on immunomodulation therapy targeting inflammatory response following acute ischaemic stroke.