Impact on clinical and cost outcomes of a centralized approach to acute stroke care in London: a comparative effectiveness before and after model

Abstract

Background: In July 2010 a new multiple hub-and-spoke model for acute stroke care was implemented across the whole of London, UK, with continuous specialist care during the first 72 hours provided at 8 hyper-acute stroke units (HASUs) compared to the previous model of 30 local hospitals receiving acute stroke patients. We investigated differences in clinical outcomes and costs between the new and old models.

Methods: We compared outcomes and costs 'before' (July 2007-July 2008) vs. 'after' (July 2010-June 2011) the introduction of the new model, adjusted for patient characteristics and national time trends in mortality and length of stay. We constructed 90-day and 10-year decision analytic models using data from population based stroke registers, audits and published sources. Mortality and length of stay were modelled using survival analysis.

Findings: In a pooled sample of 307 patients 'before' and 3156 patients 'after', survival improved in the 'after' period (age adjusted hazard ratio 0.54; 95% CI 0.41-0.72). The predicted survival rates at 90 days in the deterministic model adjusted for national trends were 87.2% 'before' % (95% CI 86.7%-87.7%) and 88.7% 'after' (95% CI 88.6%-88.8%); a relative reduction in deaths of 12% (95% CI 8%-16%). Based on a cohort of 6,438 stroke patients, the model produces a total cost saving of £5.2 million per year at 90 days (95% CI £4.9-£5.5 million; £811 per patient).

Conclusion: A centralized model for acute stroke care across an entire metropolitan city appears to have reduced mortality for a reduced cost per patient, predominately as a result of reduced hospital length of stay.

Figure 1. Stylized depiction of new and previous stroke model.

A Previous model (‘before’). B New model (‘after’). Abbreviations: A&E – Accident and Emergency Department; ASU – Acute Stroke Unit; HASU – Hyper Acute Stroke Unit; ESD – Early Supported Discharge.

Figure 2. Kaplan-Meier estimates of time from admission to hospital to death comparing ‘before’ and ‘after’.

- - - - - Before. ——— After.

Figure 3. Patients on stroke units and on the medical ward from stroke onset to 90 days after stroke.

A Before period. ——— Acute Stroke Unit. ——•— Stroke Rehabilitation Unit. - - - - - Medical ward. B After period. ——— Hyper Acute Stroke Unit. ——•— Stroke Unit. - - - - - Medical ward.

Figure 4. Cost-effectiveness acceptability curves.

- - - - - 10 years. ——— 90 days. The curves in the figure graph the probability that the new London Stroke Service is cost-effective against the cost-effectiveness threshold measured in terms of the incremental cost per QALY gained. This accounts simultaneously for uncertainty in the cost-effectiveness estimates and in the value of the cost-effectiveness threshold (the level of cost-effectiveness that the new London Stroke Service needs to be more cost-effective than, i.e., have a lower incremental cost per QALY gained than to be considered good value for money). In England the cost-effectiveness threshold used by NICE is in the range £20,000–£30,000 per QALY gained (US$31,000–£46,500 using an exchange rate of UK£1 = US$1.55). Curves are shown for each time horizon.