All primary care trusts must become world class by commissioning services that 'add life to years and years to life' and specifying the outcomes to be delivered.

Relying on historical activity within hospitals and community services will not be enough and investment decisions must address the changed financial context: an increasing elderly population, the end of unprecedented levels of government funding and patient top-ups.

World class commissioning competencies require PCTs to develop new skills in the analysis of data. A partnership between the London School of Economics and Isle of Wight PCT, funded by the Health Foundation, is pioneering a new approach to defining burden of disease - one that supports prioritisation and quantifies the expected outcome of commissioned services.

Analysis of demographic trends in the Isle of Wight, an area with a rapidly growing elderly population, shows that the need for stroke care will outstrip current capacity in all sectors. To prioritise investment, PCTs need to estimate how many people are likely to need care and the budgetary and health impacts of such provision.

Benefits and burden

Using quality-adjusted life years, we estimated the average impact of stroke on an individual as a loss of 3.7 QALYs (see first and second graphs). Scaling this up to the 490 expected stroke cases on the island in 2009, the annual loss is about 1,800 QALYs. The benefit from treatment in a specialised stroke unit compared with general wards is estimated at 0.5 QALYs per person; and about 275 patients would benefit, giving a population health impact of 150 QALY gains. But this only represents 8 per cent of the current burden. The benefit of receiving thrombolysis compared with stroke unit treatment alone is 0.3 QALYs per person; if 15 per cent of patients got thrombolysis (a very optimistic assumption), the health impact on the population would be 23 QALY gains - 1 per cent of the current burden.

Investing in thrombolysis will therefore make a minimal additional contribution to reducing the burden from stroke. More patients would benefit from receiving treatment in stroke units, which might also contribute to more efficient use of resources. But the expected gain could be doubled if accompanied by efforts to reduce hypertension through diet or prescribing (see third graph).

This example shows how scaling up expected QALY gains and comparing the impacts of primary, secondary and tertiary care can help PCTs select the most effective mix of interventions to add life to years and years to life.