The recent European Wound Management Association (EWMA) position statement on evidence in wound management (Gottrup et al, 2010), and the National Prescribing Centre bulletin (NPC, 2010) on evidence-based prescribing of wound products have heated up some old chestnuts. Evidence is ‘in’, ignorance is ‘out’! The challenge to the tissue viability lobby is either to admit that there is next to no evidence for using ‘advanced wound care products,’ or to do something to show that they are evidence-based. The NPC bulletin (2010) writes that: ‘Systematic reviews of advanced wound dressings have repeatedly highlighted the paucity of high-quality studies using clinically relevant endpoints.’
They are correctly stating the obvious, but this should not imply that such a lack exists only in wound care. A lot of what they write is adjectival: belying a non-scientific use of language. What is a ‘poor quality’ study? What would ‘high quality’ mean? What would a clinically relevant endpoint be? For the authors, a clinically relevant endpoint in a patient who shrieks with pain when her dressing is removed would be that the next dressing does not stick and that it contributes in some way to the relief of pain. Clearly, the dressing would complement investigating and treating the aetiology of the pain. Here, a suitable endpoint is pain reduction. Simple chemistry or physics would show, repeatedly and reliably, that an adhesive dressing is more likely to stick to periwound skin than one without adhesive.
Dressings are chosen by experts because they know what properties they want to exploit in particular instances, not because published data has been pooled into a metaanalysis. However, we can no longer assume that what is taken to be a foam is actually a foam (Sussman, 2010). Is there really such a thing as a generic hydrocolloid any more? So, it is likely that, whereas you can confidently state what the generic formula of aspirin is, you cannot say the same about wound care products. Thus, you are never going to compare like with like.
Until it is possible to specify what property of a dressing you are testing (moisture vapour transfer rate, acidity, etc), meaningful distinctions cannot be drawn between products. We need to know what our ‘target’ is to judge whether it has been affected or not. The endpoint called ‘wound healing’ sounds as if it is a single physiological target, but it is not. Wound management is about dealing with a sequence of multiple micro-targets. Even the doyenne of ‘evidence-based’ care had a much more nuanced view of what evidence is (Sackett et al, 1996), so must we.