What does the evidence say?
What clinical guidelines are there?
What clinical evidence is required for marketing approval?
What are the costs of wound dressings?
What does this mean for dressing choice?
What about antimicrobial dressings?
Do you have a local wound care formulary?
Choosing the most appropriate dressing for a wound requires knowledge of the safety and the clinical and cost-effectiveness of a range of dressings. It also requires careful clinical assessment of the patient's wound, their clinical condition, comorbidities, and personal circumstances and preferences. Wound dressings account for about £120million of prescribing costs in primary care in England each year, with more than £25million being spent on silver dressings alone. However, the clinical evidence supporting the use of wound dressings is less well known and of poorer quality than in many other areas of prescribing. This Bulletin explores the evidence for the clinical and cost-effectiveness of wound dressings in the management of chronic wounds, and considers the implications for dressing choice.
About 200,000 individuals in the UK, at any time, have a chronic wound (mostly leg ulcers, pressure ulcers, and diabetic foot ulcers).1 These are mostly cared for by nurses in the patient's home, in community-based clinics or in residential care.2,3 The direct cost to the NHS of caring for patients with chronic wounds has been estimated to be about £23 billion per year.1 Effective and timely diagnosis with treatment appropriate to the cause and condition of the wound, alongside active measures to avoid the incidence of wound complications and hospitalisation, can have a major impact on both costs and patient quality of life.4
In this Bulletin we consider the clinical and cost-effectiveness of advanced wound dressings (essentially those listed in BNF category A8.2), often called modern dressings, for the treatment of the most common chronic wounds in primary care. We also consider the evidence supporting the use of antimicrobial dressings (BNF category A8.3) for preventing or treating infection. We also consider the evidence for the use of dressings for diabetic foot ulcers; however, it is recommended that the management of these ulcers should be carried out by specialist multidisciplinary teams.5
This Bulletin does not consider acute or traumatic wounds, use of agents used for cleaning or debriding wounds, more specialised dressings or treatments (e.g. topical negative pressure therapy), and does not specifically consider other aspects of dressing selection or wound management generally. More information can be found on the wound care section of NPC and in the guidelines/best practice recommendations listed in Panel 1.
Panel 1: Some useful guidelines and additional materials on the management of chronic wounds
Venous leg ulcers
Diabetic foot ulcers
An overview of systematic reviews from the Centre of Evidence-Based Purchasing (CEP) in 2008 found that, of the 10 reviews relating to ulcerated wounds, few were able to draw any conclusions regarding the effectiveness of wound dressings.6 All of the reviews commented on the poor methodological quality of the included studies. There was poor reporting of assessor blinding, randomisation methods and baseline characteristics. Where conclusions could be drawn, the effect of bias could not be ruled out, and many studies of wound dressings used sample sizes too low to detect differences between treatments reliably. Recognising the paucity of good quality clinical evidence, the EWMA Patient Outcome Group has recently published a series of recommendations for the design of clinical studies in wound management to meet the need for more high-quality evidence to guide our practice in this area.7
A meta-analysis of 12 randomised controlled trials (RCTs) of chronic wounds from 2004 found that hydrocolloid dressings were more effective in healing wounds than conventional gauze dressings (odds ratio 1.72, 95% confidence interval [CI] 1.23 to 2.41).8 Likewise, a systematic review of 21 studies (20 RCTs) published in 2005,9 and an earlier review from 1999,10 both identified that hydrocolloids were more effective than conventional dressings in the treatment of pressure ulcers. However, another systematic review of 42 RCTs published in 2007 concluded that hydrocolloid dressings were no more effective than simple low adherence dressings in venous leg ulcers when used under compression (8 RCTs: relative risk [RR] for healing 1.02, 95%CI 0.83 to 1.28).11 There was insufficient evidence to draw conclusions about any differences between other types of dressings.11
Systematic reviews of mixed aetiology ulcers, arterial ulcers, diabetic foot ulcers or fungating wounds were unable to identify sufficient evidence to draw any conclusions regarding the efficacy of advanced wound dressings.6
With regard to cost-effectiveness, the CEP reviewed 29 studies comparing the costs and cost-effectiveness of advanced wound dressings. This included 13 studies in pressure ulcers, 11 in leg ulcers, and one in diabetic foot ulcers. Frequency of dressing change had the most impact on the total cost of treatment. However, it proved difficult to draw conclusions on cost-effectiveness due to the studies being of limited sample size and the narrow range of costs. Bearing in mind the limitations of the studies, hydrocolloids were considered a cost-effective option for pressure ulcers and leg ulcers compared with gauze, but there was little cost-effectiveness evidence with which to compare categories of advanced wound dressings.6
The more robust, recent evidence not considered in the CEP review is discussed below.
A pragmatic, publicly funded RCT (the VULCAN trial) compared a range of silver dressings (n=107) with a range of non-adherent control dressings (n=106) in patients with venous leg ulcers under compression bandaging or hosiery.12 There was no statistically significant difference between the silver and non-silver dressings in the primary outcome of complete ulcer healing at 12 weeks (59.6% silver, 56.7% control; RR 1.06, 95%CI 0.80 to 1.40, P=0.67). 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 health-related quality of life between groups at one, three, six or 12 months.
Economic modelling of data from the VULCAN trial found that silver dressings were associated with an incremental cost of £98, compared with control dressings, for the treatment of venous leg ulcers. 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 a greater number of dressing changes in the silver dressing group. The incremental cost-effectiveness ratio (ICER) of £489,250 per quality-adjusted life year (QALY) gained, was much higher than the threshold (£30,000 per QALY gained) typically used by NICE for establishing cost-effectiveness.12 This study and its cost-effectiveness analysis has been criticised for its relevance and generalisation to everyday clinical care, for example, patients included in the study did not necessarily have wounds that were infected or were at high risk of becoming infected.13 However, this study probably represents the best quality evidence we have at present for the use of silver dressings in leg ulcers.
A Cochrane review of 25 RCTs assessing antibiotics and antiseptics for venous leg ulcers (including 21 trials of topical antiseptics) identified some evidence to support the use of topical cadexomer iodine in leg ulcers.14 One study showed a statistically significant result in favour of cadexomer iodine when compared with standard care (not involving compression) in the frequency of complete healing at six weeks (RR 2.29, 95%CI 1.10 to 4.74). When cadexomer iodine was compared with standard care, with all patients receiving compression, the pooled estimate from two trials for frequency of complete healing at four to six weeks indicated significantly higher healing rates for cadexomer iodine (RR 6.72, 95%CI 1.56 to 28.95).
A Cochrane review of honey as a topical treatment for wounds identified only two RCTs in venous leg ulcers (n=476).15 Use of honey as an adjuvant to compression did not significantly increase leg ulcer healing at 12 weeks (RR 1.15, 95%CI 0.96 to 1.38, P=0.12) compared with controls (usual care or hydrogel dressings). However, adverse events were significantly more common in the honey treated group (RR 1.27, 95%CI 1.05 to 1.55, P=0.016).
A systematic review of treatments for pressure ulcers identified 54 RCTs evaluating absorbent wound dressings.16 Most of the trials had poor methodology. Generally, no one dressing was found to be superior to another, although one good quality study found that calcium alginate dressing improved wound healing compared with dextranomer paste.
Another systematic review of 28 RCTs of hydrocolloids for the treatment of pressure ulcers identified significant efficacy and cost advantages for hydrocolloid dressings over gauze dressings. However, hydrocolloid dressings appeared to be more costly and less effective than some other advanced dressings.17
Diabetic foot ulcers
An RCT of 134 patients with non-ischaemic diabetic foot ulcers compared a hydrofibre dressing containing silver with a calcium alginate dressing.18 There was no statistically significant difference in the primary endpoint of healing speed (silver dressing 11.6% per week, alginate 10.0% per week; P=0.99) or in the mean time to healing (53 vs. 58 days, respectively, P=0.34). During the study adverse events related to clinical infection were similar (16% with silver dressing and 12% with alginate dressing).
A publicly funded, observer-blinded RCT of 317 patients compared three widely used dressings: a simple non-adherent dressing, an iodine dressing, and a hydrofibre dressing in patients with chronic diabetic foot ulcers.19 No significant difference between the dressings was found in terms of the percentage healed by 24 weeks, the mean time to healing, quality of life, or adverse events. Non-adherent dressings were associated with least pain at dressing changes. However, more patients withdrew from the study who received the non-adherent dressings (35% non-adherent vs. 29% hydrofibre, 19% iodine; P=0.038). Health economic analysis found that the use of hydrofibre dressings was associated with significantly higher cost, which was not offset by fewer dressings being required (mean cost per patient: £44 hydrofibre, £17 iodine, £15 non-adherent). The authors concluded that, as there was no difference in effectiveness, there was no reason why the least costly of the three dressings could not be used more widely across the NHS.
A Cochrane review of silver dressings for the treatment of infected wounds from 2007 identified only three RCTs with a short follow-up of 4 weeks.20 None of the trials demonstrated clear evidence of the effectiveness of topical silver in terms of increased healing rate, and the authors considered that there was insufficient evidence to recommend the use of silver containing dressings in the treatment of infected or contaminated wounds. Although a subsequent systematic review of 14 studies indicated benefits for silver dressings for some outcomes in infected chronic wounds, many of the studies were of low quality (only five were RCTs) and subject to bias.21
A Cochrane review from 2010 of topical silver products (dressings or creams) for preventing wound infection identified 26 RCTs, 20 of which were on burns.22 Most of the trials were small and of poor quality. Overall, the authors of the Cochrane review considered that there was insufficient evidence to support the use of silver-containing dressings or creams, as generally they did not promote wound healing or prevent wound infections.
A number of clinical guidelines and 'best-practice' recommendations for the management of chronic wounds have been developed, based on reviews of the clinical evidence and expert consensus (see Panel 1).
The RCN guideline for the management of patients with venous leg ulcers (2006) states that the most important aspect of treatment for uncomplicated ulcers is the application of high compression using a stocking or bandage. In the absence of evidence to promote use of any particular dressing, dressings should be simple, low adherent, low cost and acceptable to the patient.23 The CKS topic on the management of venous leg ulcers, is largely based on this guideline, and gives pragmatic advice on dressing selection.24
The NICE clinical guideline on the management of pressure ulcers (CG29, 2005), developed by the RCN, identified insufficient research to guide clinician's decision making about which dressings are more effective in pressure ulcer management. On the basis of professional consensus, NICE recommends modern dressings (e.g. hydrocolloids, hydrogels, hydrofibres, foams, films, alginates, soft silicones) to create the optimal wound healing environment in preference to basic dressings (e.g. gauze, paraffin gauze, simple dressing pads).25
The NICE clinical guideline for prevention and manage-ment of foot problems in type 2 diabetes (CG10, 2004) recognises the important role that healthcare professionals in primary care have for assessing risk and referring patients to a specialist foot care team within 24 hours where there is new ulceration, swelling or discolouration.5 No specific recommendations are made with regard to dressing selection.
Dressings are generally classified as medical devices. This is the case even for antimicrobial dressings, provided the antimicrobial agent is considered to provide an ancillary action on the wound.6
In accordance with the Medical Devices Directive (93/42/EEC), dressings must meet the applicable 'essential requirements' on safety and performance.26 Clinical data are usually necessary to demonstrate satisfactory performance of a medical device and establish any adverse effects. However, unlike medicines, where data from RCTs are generally required, for devices this can take the form of a review of the relevant scientific literature and clinical trial data are not always required.27 Standard laboratory performance tests are required that measure the physical properties of dressings (e.g. absorbency, moisture vapour transmission, waterproofness, conformability, etc.). These cannot predict reliably how dressings will perform in the clinical situation.6
Although only representing one route by which dressings are procured for use in the NHS, the prescription costs for wound dressings in primary care in England were about £116 million in the year to September 2009.28 A breakdown of the number of items prescribed and their costs according to the BNF category of dressing is shown in Figure 1. There is considerable variation in the cost of dressings both between categories and within each category. Silver containing dressings accounted for about 11% of items supplied on prescription, but in view of their relatively high cost were associated with 22% (£26 million) of the total cost of advanced wound dressings.
Safety, efficacy and cost-effectiveness are important factors to consider when choosing dressings. However, a decision on which dressing is most appropriate for a specific chronic wound also requires careful clinical assessment of the patient's wound, their clinical condition, any comorbidities and their personal circumstances and preferences. As reviewed in this Bulletin, there is little high-quality evidence from RCTs, or systematic reviews of controlled clinical trials on which to base dressing selection. What evidence there is suggests that there is little difference in efficacy between any of the advanced dressings for healing of chronic wounds.
Although there is reasonable evidence that hydrocolloid dressings are more effective than conventional gauze dressings in treating pressure ulcers, there is no evidence that they are more effective than simple low-adherent dressings when used under compression for the treatment of venous leg ulcers. Evidence from systematic reviews strongly suggests that sustained compression therapy is particularly effective in treating venous leg ulcers, making it difficult to observe further improvement as a result of dressing usage.7
Where a specific dressing cannot be adequately justified on clinical grounds, it would seem appropriate for NHS health professionals to routinely choose the least costly dressing of the type that meets the required characteristics (e.g. size, adhesion, conformability, fluid handling properties, etc.) appropriate for the type of wound and its stage of healing.
Antimicrobial dressings account for about a quarter of the dressings prescribed in primary care in England.28 Silver dressings, in particular, have grown in popularity without an evidence-base to support this increasing use. As pointed out in a recent review article on silver dressings, "marketing and promotional issues occasionally obscure the evidence that clinicians need to have in order that they may provide appropriate treatment for their patients".29 In view of the lack of high quality trials to establish advantages over other, cheaper, alternatives, a recent Drug and Therapeutics Bulletin concluded that "the routine use of silver dressings is not justified on clinical or cost-effectiveness grounds as treatment for uncomplicated leg ulcers, when simple dressings and compression bandaging are more appropriate".30 CKS has taken a similar view in its clinical topic on venous leg ulcers.24
Clinically uninfected wounds that are healing as expected do not require topical or systemic antimicrobials.31 Clinically infected wounds usually require systemic antibiotic therapy, and topical antimicrobial dressings may be appropriate. 32 Early recognition of infection and intervention in chronic wounds to avoid complications is important; this is particularly the case for diabetic ulcers.29 However, there is controversy over how to define wound infection, whether microbiological studies are useful, and how to treat poorly healing wounds with 'secondary' signs of local infection (e.g. nonpurulent exudation, discoloured or friable granulation tissue, breakdown or 'pocketing' at the wound base, or an abnormally foul odour).31
There is some evidence that cadexomer iodine used under compression, may be effective in improving the healing of venous leg ulcers. However, there is no robust evidence from RCTs that antimicrobial dressings containing silver, iodine or honey are effective in preventing or treating infection in chronic wounds. Topical antibiotics, should generally be avoided to minimise the risk of allergy and the emergence of bacterial resistance.32
As well as the cost implications and lack of robust evidence for their benefit, indiscriminate use of topical antimicrobial dressings should also be discouraged because of concerns over bacterial resistance and toxicity,32, 33 Long-term use should be avoided,34 and they should be discontinued when signs of infection resolve, when the wound starts to heal or if the patient experiences adverse effects from the antimicrobial.32
In view of the multitude of dressings available, the absence of specific advice in national guidelines, and recognising financial constraints, local formularies provide a means of rationalising choice of dressings.
According to the Wounds UK Best Practice Statement,35 formularies should be developed by multidisciplinary teams using a fair and impartial process, avoiding the undue influence of the manufacturers. They should include a range of clinically and cost-effective products to serve the range of wound types and stages of healing. In the absence of clinical and cost-effectiveness evidence to distinguish between dressings of similar type, and in the absence of other clinically important differences, acquisition cost is an appropriate deciding factor in choice of dressings. One selection process, adopted for the development of the Northern Ireland wound care formulary36 is that of Safe Therapeutic Economic Pharmaceutical Selection (STEPS).37
Figure 1: Annual prescribing volumes (A) and costs (B) of advanced wound dressings in primary care in England (October 2008 to September 2009). Figures created from data provided by the NHS Business Services Authority.28
The National Institute for Health and Clinical Excellence (NICE) is associated with MeReC Publications published by the NPC through a funding contract. This arrangement provides NICE with the ability to secure value for money in the use of NHS funds invested in its work and enables it to influence topic selection, methodology and dissemination practice. NICE considers the work of this organisation to be of value to the NHS in England and Wales and recommends that it be used to inform decisions on service organisation and delivery. This publication represents the views of the authors and not necessarily those of the Institute.
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