Redirecting patients to improve stroke outcomes: implications of a volume-based approach in one urban market

The designation of primary stroke centers may result in patients being redirected from their usual source of care, although there is little evidence that these centers would result in better outcomes or lower costs. An alternative approach could direct patients to hospitals treating greater volumes of stroke patients.

We sought to estimate the effect of hospital stroke volume on patient mortality and costs in a regional hospital market and to analyze the implications of hypothetical volume-based referral policies in that market, including the effects of patient-hospital distance.

Using a retrospective cohort, we studied 12,150 Medicare patients admitted for acute stroke to 1 of 29 hospitals in Greater Cleveland during a 7-year period. The primary outcome was risk-adjusted 30-day mortality. Secondary outcomes included log hospital costs and discharge destination. The primary measure of volume was average annual number of stroke patients; patient distance to the nearest hospital was approximated using patient zip code and hospital address data.

Overall 30-day mortality was 14.9%. For each 100-patient increase in hospitals' annual stroke volume, risk-adjusted mortality declined 0.9 percentage points (odds ratio = 0.90; 95% confidence interval = 0.82-0.98; P < 0.02) with no significant difference in hospital costs. For each 1-mile increase in patient distance to nearest hospital, mortality increased 0.6 percentage points (odds ratio = 1.07; 95% confidence interval = 1.03-1.11; P < 0.01). Only 3 of 29 hospitals (10.3%) exceeded the highest plausible threshold (250 strokes/year), redirecting 81.4% of patients for a net reduction in mortality of 0.4%; lower thresholds would redirect fewer patients but have negligible effects on mortality.

Our findings fail to support redirecting acute stroke patients based on hospital stroke volume.