Measuring success in venous ulcer healing: “Ambiguous and difficult to define”

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Defining success in venous ulcer healing, and for all chronic wounds, remains a nebulous concept—with no consensus on what constitutes a successful outcome. Dave Bosanquet (Bristol, UK) outlined the difficulties at the Charing Cross Symposium (CX; 15–18 April, London, UK), arguing that a “core outcomes set” was needed to help characterise success.

Systematic reviews of wound healing literature have found that “over 100 different outcomes are being reported in the randomised controlled trials (RCTs)”, said Bosanquet, asking: “How do you pick the outcomes that are meaningful, clinically relevant and important to patients? In order to address such variation, the key thing that is needed is a core outcomes set—a core outcomes set is where you decide what outcomes are so important that they should be reported in all trials involving wound care.”

The Food and Drug Administration (FDA) definition of wound healing has been widely accepted as the industry gold standard, defined as 100% re-epithelialisation of a wound surface, without exudate, drainage or dressing, that is confirmed, once healed, two weeks later. “RCTs and cohort studies are good at reporting the first two aspects,” Bosanquet pointed out. “What we are not good at doing is checking that those wounds do not reoccur after a couple of weeks.”

Surrogate outcomes are also used to define endpoints: “Wound healing is a complex process comprising a number of stages. It is not just complete closure—you have a lot of studies that report an outcome of a 50% reduction in wound size after four weeks […] we are talking about surrogate outcomes. Rather than the end outcome of actual wound healing, you are evaluating a half-way outcome. And we know that wounds do not necessarily heal in a linear fashion, and that the percentage change can be exaggerated when we look at small wounds compared to large wounds. We have also got to recognise that some wounds are never going to heal.”

Measures can be based on efficacy, efficiency or effectiveness, broadly referring to healing (and recurrence), the speed at which that happens (the number of visits, time to heal, and number of dressing changes), and the cost, both financial and to the patient. They can also be grouped into symptoms, such as exudate, oedema, odour and pain, quality of life measures, patient preference and acceptability, resource usage (in terms of staff time, number of visits, cost), and the tissue type: granulation or necrosis.

“When we have all these varying outcomes, how on earth do we synthesise the data? How do we perform meaningful meta-analysis?” he asked.

He highlighted comments from the European Wound Management Association which states, “if the only gold standard was total wound closure, no therapy would ever be considered efficacious,” and adds: “Conversely, if a non-specific endpoint is chosen, any positive findings may not translate into a clear clinical benefit at the bedside.”

Development of a core outcome set for chronic wounds including venous ulcer healing involves an exhaustive systematic review to summarise outcomes currently being reported, then gathering together a large group of key individuals comprising patients, healthcare professionals and industry, “and through a Delphi process achieve consensus on what are the actual outcomes that are important to report for patients undergoing clinical trials”.

Bosanquet concluded: “Healing itself, as defined by the FDA, is generally well done in the literature, with the exception of checking that your wound has not recurred after a couple of weeks. Surrogate outcomes, such as a 50% area of reduction after a few weeks, are done quite frequently, but have inherent problems, as all surrogate outcomes do. There are a number of other outcomes, inconsistently reported, which make comparison difficult. We await the results of the core outcome set to help decide how we should define success in wound healing.”


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