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Wound-bed preparation is considered the gold standard for chronic non-healing wounds, particularly venous leg ulcers. Several systematic reviews and meta-analyses have studied silver dressings as innovative treatment products designed to control and inhibit infection and provide an environment conducive to wound healing. At the same time, cost savings and improved effectiveness are concerns in clinical wound treatment. There is little literature on the cost-effectiveness of silver dressings versus other approaches to treating lower leg venous ulcers.
Michaels and colleagues set out to determine whether there is any significant reduction in treatment costs or increase in wound healing rate among patients with lower leg venous ulcers when silver-based dressings rather than non-silver dressings are used. The study design was a multicentre randomised (stratification according to ulcer size and treatment centre) controlled study with concealed allocation lasting 12 weeks in two geographical areas in South Yorkshire and Devon, UK. The sample was 213 patients (experimental group: mean age 68.8 years; control group: mean age 72.4 years) who had had active venous leg ulceration for longer than 6 weeks. Exclusion criteria included insulin-controlled diabetes mellitus, pregnancy, sensitivity to the use of silver, ankle brachial pressure index <0.8, ulcer area <1 cm, vasculitis, and oral or parenteral antibiotic treatment. Patients were treated with either silver-donating dressing (Urgotul SSD, Aquacel Ag, n=107) or non-silver, low-adherence dressing (Urgotul, Biatain, Atrauman, Allevyn, n=106). Both groups used secondary dressing with multilayer compression, 7-day change. The primary outcome was complete ulcer healing at 12 weeks; secondary outcomes included time to healing, quality of life (QOL) (EQ 5D, short form 6D) and cost-effectiveness over 6 months and 1 year.
The incremental cost-effectiveness ratio for the experimental group was £489.250 per quality-adjusted life year gained. The authors concluded that there were no significant differences in primary or secondary end points and that there were no significant improvements in effectiveness or cost savings through the routine use of silver-donating dressings on lower leg venous ulcers.
The strengths of the trial include the large, multicentre sampling from two geographical areas and a focus on specialists in leg ulcer clinics offering primary care. Advantages of the trial include random allocation, use of non-silver, low-adherence dressing in the control group, and blinded and intention-to-treat analysis in the assessment of outcomes. The sample was sufficiently large to estimate any clinically important difference in healing time. The 12 weeks' follow-up was appropriate for assessing healing outcomes and adverse events. Furthermore, this study's assessment of QOL and cost-effectiveness at 6 months and 1 year after treatment offers a valuable insight into wound management.
Concerns about the trial include failure to identify the clinical trial intervention protocol, such as how the wound bed was cleansed, who carried out the intervention and who made the primary outcome measurement. Although silver-donating dressings can control the superficial bacterial burden on wounds at risk of developing infection, this study lacked detailed description of the wound bed's colonised status. In addition, the trial's confounding variables included the use of six types of silver-donating dressing with differences in description and indication, for example the Aquacel Ag (Convatec) dressing with hydrofibre (sodium carboxymethylcellulose) with 1.2% silver for moderate to highly exudates and Contreet foam silver-release dressing consisting of a soft hydrophilic polyurethane foam for medium to heavily exudates. In addition, the study recruited only patients with lower leg venous ulcers whose ankle brachial index was >0.8. Clinical wound specialists are cautioned about applying the results to mixed-type leg ulcers.
Previous randomised controlled trials or systematic reviews and meta-analyses support silver-donating dressings for the treatment of contaminated and infected acute or chronic wounds on the basis of reductions of wound area, malodour, wound exudates and wound pain and of improvements to patients' QOL and dressing wear time. However, the study by Michaels and colleagues provided no evidence to support effectiveness and cost savings for routine use of silver dressing. The development of a disease-specific QOL indicator for patients with lower leg ulcers might provide better sensitivity for assessing significant differences in outcome. Further research is needed to test the cost-effectiveness of silver-donating dressing for improving wound healing in the treatment of venous ulcers.
Competing interests None.
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