Value in pathways versus value in populations – Don’t forget population health in your efforts to improve “efficiency”. Its important but remarkably easy to forget

Value in pathways versus value in populations – Don’t forget population health in your efforts to improve “efficiency”. Its important but remarkably easy to forget


A 2014 UCL study published in the BMJ[i] provided some fascinating evidence on the potential impact of stroke centralisation. This was essentially an n=2 study using data from two sites. The media coverage was equally interesting[ii]. In essence the study found that comprehensive overhaul of services focused on centralising care to eight (rather than 30) sites will save lives; and by extension less far reaching reform (in the study using Manchester data) achieves less impact.


This is a fascinating study. It is very heartening to see high quality systems research, something we need more of. One might conclude that such an approach to centralising stroke care leads to a more efficient stroke system.


A simple calculation based on the abstract – where an absolute risk reduction (centralised vs current) of approx 1% leads to an estimation that you need to have a volume of 100 or so patients going through centralised care (compared to current) to prevent one additional death (NNT =c100).


Given the study considered two sites, one can readily draw a conclusion that we should be minded to not generalise too quickly from Manchester and London to other places in the UK.


It is of note that the Morris study did not seem to factor in the costs of centralisation. Obviously there ARE inherent cost of the reconfiguration. Later evidence[iii] has suggested the cost of the London stroke strategy was £23m the lions share of which goes into acute and hyper acute stroke care, and that a similar investment was not made in Manchester, nor is it planned elsewhere. Furthermore one may never actually realise the benefit of this in cold hard cash unless you ACTUALLY take the capacity OUT of the system etc and politics of closing smaller units. There may also be knock on consequences. The authors had subsequently noted (in their response to commentators) that a full economic analysis is planned. This MUST be factored into any subsequent economic analysis.


One of my final reflections on this study is that arguably the central point of centralisation is to speed the time to thrombolysis, and prevention of downstream disability (and death). It is always important to recall that the evidence around the clinical effectivness of alteplase as a thromboltic agent remains contested[iv] [v] [vi], and there is a wealth of audit and other published data suggesting that that the vast majority DONT get thrombolysed rapidly enough. Maybe centralisation will improve this.


A population perspective

However, there is also an alternative perspective from which one might view this. The Morris study makes a case for centralisation being one tool to improve the efficiency (cost and outcomes) of those treated with acute stroke. An alternative perspective might be to consider the population burden of stroke disease and the most efficient strategies to address this. Arguably this is considerably more important than actute stroke care as the NHS is responsible for meeting CURRENT needs now and future needs (the currently at risk population).


Previous work conducted on Isle of Wight about the population benefit of different methods of achieving a reduction in morbidity associated with stroke (an earlier version of STAR tool[vii]) essentially begin to build a methodology to compare the health gain of different methods of reducing stroke morbidity – ie comparing hyper acute stroke unit with population BP control.


What should you do for most health gain if time and resources are limited.

An argument can easily be made that if the objective of the health care system is the reduction of morbidity and mortality from stroke – ie the stroke burden of disease then it may be considerably more beneficial in pop health terms to focus your energy on primary prevention of stroke.


This might especially be the case if and there is limited time, attention (policy makers, clinicians and commissioners) and cash to effect improvement.


From a population health perspective the most obvious targets are HTN prevention (particularly perhaps population approaches to salt in processed food), aggressive clinical management of known hypertensive population and improving anticoagulation rates in AF. This line of argument was quantified in a 2011 LSE paper[viii]. Though the LSE paper DID find that treatment in centralised units is an important strategy for reducing burden of disease – most to all of the subsequent policy attention has been given to this strategy, arguably this is at the expense of population prevention.


This story illustrates a number of important points.

There is an important distinction between an approach to technical efficiency focused on cost and outcome in those that are treated (the classical approach to technical efficiency), versus those treated AND those at risk (a more contemporary approach to population value)


This story underscores:

The importance of a whole population perspective

the importance of scale, and

the benefits of prevention vs treatment


The costs of all competing options needs to be factored in. there is increasingly good evidence on the effectiveness of clinical interventions[ix] to achieve population health goals and combined clinical and public health approaches[x].


I am NOT arguing that we SHOULNT improve acute stroke care. However, I AM arguing that we should not forget these basic lessons and our continued under implementation of prevention in our rush to “transform our health care system”.









[vii] LSE / Health Foundation. STAR – socio-technical allocation of resources.

[viii] LSE working paper no 5. Estimating the health gains and cost impact of selected interventions to reduce stroke mortality and morbidity in England. 2011. M Airoldi, G Bevan, A Morton, M Oliveira and J Smith


[x] CDC CMS Million Hearts Initiative



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