11 November 2009
The VULCAN study found no evidence to support the use of silver dressings under compression bandaging for the treatment of venous leg ulcers. Compared with non-silver low-adherent dressings, silver dressings were not more effective in healing ulcers, did not improve quality of life, and were not cost-effective.
Level of evidence:
Level 2 (limited quality patient-oriented evidence) according to the SORT criteria.
Healthcare professionals should follow CKS guidance for the management of leg ulcers. Routine use of silver-containing dressings under multilayer compression bandaging is not recommended for the treatment of leg ulcers. In the absence of any evidence for a clinical benefit or cost-effectiveness advantage, healthcare professionals should not use them ahead of less-expensive non-silver wound dressings.
What is the background to this?
Several systematic reviews (see ‘How does this relate to other studies?’ below) have pointed out the lack of good quality clinical evidence to support the use of modern wound dressings, including the relatively more expensive silver dressings. They highlight the need for prospective randomised controlled trials (RCTs) to evaluate their effectiveness. This publicly funded, pragmatic RCT sought to address the lack of evidence by examining the effectiveness and cost-effectiveness of silver dressings applied beneath compression bandaging in the treatment of venous leg ulcers.
What does this study claim?
The VULCAN study randomised 213 patients to silver-donating dressings (n=107) or non-antimicrobial, low-adherence dressings (n=106). Dressings were changed at least weekly and were covered by multilayer compression bandaging. No evidence was found to support the routine use of silver-donating dressings beneath compression for venous ulceration.
There was no statistically significant difference between the silver and non-silver dressings in the primary outcome of complete ulcer healing after 12 weeks (59.6% silver, 56.7% control; relative risk [RR] 1.06, 95% confidence interval [CI] 0.80 to 1.40; P=0.67) after six months, or after one year. Overall median time to healing was 67 days for the silver dressings and 58 days for control dressings (P=0.41). There was no significant difference in quality of life (EuroQol 5D and Short Form 6D) between groups at any of the follow up times of 1, 3, 6 and 12 months.
Compared with the control group, the silver dressing group had an incremental cost of £98 and an incremental quality-adjusted life year (QALY) gain of 0.0002, giving an incremental cost-effectiveness ratio of £489,250 per QALY gained for the silver dressings. The additional costs for the silver dressing were partly due to an increased cost of dressings (£31 vs. £6 per patient), but also due to an increase in the number of dressing changes in the silver dressing group.
How does this relate to other studies?
A 2006 Cochrane Review of wound dressings used underneath compression bandaging for the treatment of venous leg ulcers found no, or insufficient, evidence that any one dressing type was better than another with regard to ulcer healing. A previous Rapid Review blog from 2007 considered a systematic review of modern wound dressings for the treatment of acute and chronic wounds. It pointed out the lack of good quality clinical evidence to support the use of modern wound dressings, including the relatively more expensive silver dressings.
A Cochrane Review from 2007 specifically considered the use of silver-containing dressings for treatment of infected or contaminated chronic wounds. Only three trials with a short follow-up duration were found, and insufficient evidence was found to recommend the use of silver-containing dressings or topical agents.
A meta-analysis of the effectiveness of silver-releasing dressings in the management of infected chronic wounds identified some positive effects for silver-containing wound dressings. However, the quality of the trials was limited by the potential for bias associated with inadequate concealment, no detailed description of the outcome measurement and no reported intention-to-treat analysis. Moreover, problems existed in some studies with confounding factors.
Silver dressings are one of the many ‘modern’ or ‘advanced’ dressings available in the UK. Silver is included as an anti-infective agent. There are many silver dressings available and they are expensive; the cost to the NHS on FP10s alone in the year to September 2008 was about £25 million, compared with costs about of £110 million for all wound management dressings.
The results of this study suggest that, when used under compression bandaging, silver-containing dressings are not more effective than unmedicated non-adherent dressings in healing leg ulcers, are not associated with a better quality of life, and are not cost-effective.
In the absence of demonstrating any significant advantage over non-silver containing dressings (i.e. efficacy, safety, patient factors) that might justify their use ahead of less costly non-silver containing dressings, routine use of silver-containing dressings cannot be recommended.
The results of this study are consistent with CKS guidance (last revised 2008) on the management of venous leg ulcers, which points out that ‘there is insufficient evidence to show that any wound dressing (including dressings impregnated with silver) is better than simple low-adherent dressing for the healing of venous leg ulcers’. Healthcare professionals should follow this CKS guidance, which broadly follows 2006 guidance from the Royal College of Nursing Institute.
There are some significant limitations of the study, some of which are discussed by the authors of the paper. These need to be considered when interpreting the results of the study. The lack of blinding of treatment to those providing and assessing the treatments is a major limitation. Also, many types of dressing were used in the study, and it is not known whether there are any advantages of any individual dressing over another (silver or non-silver). Although the study suggests no general benefit of including silver in the dressings, specific clinical trial data is needed to confirm that this is the case for all dressings, which may differ in their characteristics. There were also variations in demographics and healing rates between the two centres, who used a different mix of silver dressings and where wound-care practices may have varied; this may have introduced bias into the study. Despite these limitations, this study is the best evidence we have for the effectiveness of silver dressings in wound care. The study suggests that their routine use is not justified on clinical or cost-effectiveness grounds for the treatment of leg ulcers under compression bandaging. Further well controlled studies are needed to justify their use ahead of non-silver dressings for managing other types of wounds.
More information on alternative types of advanced wound dressings that are available in the UK and the (limited) clinical evidence supporting their use can be found in Advanced Wound Dressing Buyers’ guide produced by the Centre for Evidence-based Purchasing.
Michaels JA, et al. Randomized controlled trial and cost-effectiveness analysis of silver-donating antimicrobial dressings for venous leg ulcers (VULCAN trial). Br J Surg 2009;96:1147–56
Multicentre, pragmatic, prospective, randomised controlled study carried out in two regions of England.
The study recruited 213 patients with active ulceration of the lower leg that had been present for more than six weeks. 53% reported previous episodes of leg ulceration, 21% had deep vein thrombosis and 55% had a history of varicose veins. The mean ages were 69 years in the silver dressing group and 72 years in the control group.
Intervention and comparison
Patients were randomised to receive silver-donating dressings (n=107) or non-antimicrobial, low-adherence dressings (n=106) for 12 weeks. A variety of silver and non-silver dressings types were used according to normal practice beneath multilayer compression. The type of silver dressing was the clinician’s choice from an approved list of six dressings. The non-silver dressings were standard non-antimicrobial low-adherence dressings from any manufacturer (82% were low-adherence knitted viscose dressings). Allocated dressings were applied at each dressing change (at least weekly). Other interventions or treatments could be used (e.g. debridement) if felt to be clinically appropriate. If there was still ulceration after 12 weeks, the clinicians caring for the patients decided whether or not to continue or change the dressings. All patients were followed up for 12 months.
The perspective for the cost-effectiveness analysis was that of the UK NHS and Social Services, will all costs reported in 2007 prices.
Outcomes and results
Analysis was by intention to treat. There was no statistically significant difference between the dressings in the primary outcome of complete ulcer healing after 12 weeks (59.6% silver, 56.7% control; relative risk [RR] 1.06 95%CI 0.80 to 1.40; P=0.67). There were also no significant differences at six and twelve months, Overall median time to healing was 67 days for the silver dressings and 58 days for control dressings (P=0.41). Among the 185 patients whose ulcers healed within the first year, 24 (11 silver, 13 control) had recurrent ulceration. There was no significant difference in quality of life (EuroQol 5D and Short Form 6D) between groups at any of the follow up times of 1, 3, 6 and 12 months.
The biggest single contributor to costs for both groups was the cost of attending clinics, accounting for 61–66% of the total costs. The mean cost per clinic visit for the silver group was £275 compared with £196 for the control group. The mean cost of silver dressings was £30.62 compared with £5.73 for the control dressings. The mean total cost per patient was £418 for the silver group and £320 for the control group (an incremental cost increase of £98). Compared with the control group the silver dressing group had an incremental QALY gain of 0.0002, giving an incremental cost-effectiveness ratio of £489,250 per QALY gained for the silver dressings.
The trial was funded by the NHS Heath Technology Assessment Programme.
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