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Analysis of THIN data compares treatment options for exuding chronic venous leg ulcers in terms of cost-effectiveness

17th April 2013

Panca M, Cutting K, Guest JF (2013) Clinical and cost-effectiveness of absorbent dressings in the treatment of highly exuding VLUs. J Wound Care 22(3): 109–118

Superabsorbent dressings contain sodium polyacrylate and are designed to be used on moderate to highly exuding wounds. This study involved estimating the cost-effectiveness of four superabsorbent dressings when used on highly exuding chronic venous leg ulcers.  The superabsorbent dressings that were assessed were Dry Max Extra (Absorbest AB) KerraMax (Crawford Healthcare), Flivasorb (Lohmann & Rauscher) and sachet S (Sorbion). Another dressing that is commonly used for these type of wounds was also included in the study — Aquacel (ConvaTec), which is made of sodium carboxymethylcellulose.

The authors used the Health Improvement Network (THIN) database to access information on patients who had used the dressings under scrutiny. THIN is reported to be representative of the UK demographic and includes information on more than 9 million patients. The database includes patients’ entire medical histories. Adult subjects were selected at random from the database if they had a VLU that had lasted 3 months or more before treatment, had not been treated with any of the comparator dressings at least 6 months before being treated with the dressing under question had 6 months follow-up information included on the database. Each group was matched according to age, gender, their general practice, date of diagnosis of their VLU and the start date of their treatment. Each group had 99 participants apart from DryMax which had 43 because 57 were excluded because they had underlying skin cancer.  The study cohort was 439. Six months of treatment data were compared. If wound size measurements were not available, it was estimated to be 80% of the dressing size. Statistical significance was tested and logistic progression performed to assess the impact of the wound’s baseline characteristics. A decision model was created and compared the results. Unchanged, improved, worsened, healed and death were used as parameters. Quality-adjusted life years (QALYs) were also estimated. A cost of treatment was calculated using unit costs for 2010/11 and calculated for the six months of treatment being studied. Cost-effectiveness was calculated by relating the actual cost to the QALYs so comparisons were made on the cost per QALY gained. A dressing was considered to be the dominant treatment if it gave an improved outcome for less money spent on treatment. Cost-effectiveness acceptability curves tested the reliability of the data using bootstrapped subsets. Deterministic sensitivity analyses was also performed to see if the cost-effectiveness of a single strategy over another would vary using different parameters in the model. Healing was ranked of high importance along with frequency of dressing change. Pain levels during dressing change and wound healing times were also considered but given a lesser priority based on a methodology from a previous study. Aquacel was excluded from the cost analysis as wounds that did not heal after treatment with Aquacel increased in size by 43% whereas the other treatment options saw unhealed wounds decrease by 34% during the study period.


Two main differences were identified in the groups under study: the size of VLUs treated with CMC were significantly smaller than the other groups, and wounds treated with sachet S were significantly older.

The authors acknowledge the study’s limitations, mentioning underreporting of visits on the THIN database, the 6-month cut-off period and the fact that a lot of data that would have illustrated the effects of healing time were not always included in the study. It was also reliant on the data entered by disparate clinicians and the accuracy could not be validated in every case. However, the authors conclude that sachet S appeared to be more effective than the other dressings in the study for the treatment of highly exuding chronic VLUs and its use was less costly. It was £3800 for a 6-month period of treatment with sachet S and this was 15–28% lower than the others. The patients treated with sachet S accrued 0.3–3% more QALYs. The authors ranked the other dressings as DryMax, Flivasorb, Kerramax and then Aquacel. The authors say that this study should be used as a basis for RCTs comparing superabsorbent dressings. It was acknowledged that this study was funded by the manufacturers of sachet S although the authors maintained that the study was carried out independently.

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