Shirley McIver's article on expert patients ('So you think you know it all?' pages 22-23, 16 September), though clearly well informed, misses some crucial issues.

The NHS sometimes needs reminding that patients, people, and more particularly communities, are already the co-producers of their own health, illness, treatment and rehabilitation. What expert patients need is an infrastructure of communication available where people live, work or play - in communities, families and workplaces. Such resources should be made available long before they need to access the healthcare system.

To address this we need direct, earthy and connected relationships between patients - a decentralised and non-hierarchical Celtic church structure of support, not one mediated through the bishops, priests, confessionals and cathedrals of the healthcare system itself.

For many of the 'new diseases' - allergies, ME etc - medical and patient definitions of both problem and solution are increasingly divergent.

We do not have to think too hard to guess whose views will predominate and what the consequences might be. It is not so much that 'knowledge is power' but that 'power is knowledge' in the healthcare system. It is this issue which will sink expert patients' programmes if this important initiative is not thought through properly.

Evidence underpinning medical and therapeutic intervention in disease is an applied science. It requires judgement in its application. Judgement depends on values. Giving privilege to one judgement or set of values against another requires power. The meaning and importance of evidence is thus really about choices based on experience or interests. Patients have experience and the system has interests. Which choice is taken depends on who among the stakeholders has the greater positional power. This in turn is mediated through the micro-political structure of the healthcare system itself.

For this reason, the Department of Health might be well advised to place the organisation and management of the expert patients' programme as far away from the healthcare system as it can get it.

Dominic Harrison

Deputy director

Public health and health professional development unit

Lancaster University