5.1 None of the identified published studies contained cost information relating to the Debrisoft pad. The Soares (2009) study, which reported results from the VenUS II trial, was used to provide clinical effectiveness information for the comparators in the cost analysis.
5.2 The sponsor submitted a de novo cost analysis that estimated the costs and resource consequences of using the Debrisoft pad in a community setting compared with hydrogel, gauze and larvae. Full details of all cost evidence and modelling considered by the Committee are available in the assessment report overview.
5.3 The sponsor submitted a base-case analysis for 2 community settings: a community-based clinic and home (including a residential or nursing home). The population was adults and children needing debridement of an acute or chronic wound. A single cost analysis was provided in the sponsor's submission to account for all debridement; no distinction was made between adults and children, or between acute or chronic wounds.
5.4 Clinical effectiveness information for each product was used to inform the 'number of applications to complete debridement' parameter in the cost analysis. Data from the VenUS II trial (Soares et al. 2009) were used to represent the effectiveness of larvae and hydrogel. The effectiveness of gauze was based on clinical opinion obtained by the sponsor. The effectiveness estimate for the Debrisoft pad was obtained from the Bahr et al. (2011) study. The design of this study limited the number of applications of the Debrisoft pad to 3. Results from this study showed that 77% of wounds were completely debrided after 3 applications. In the cost analysis the remaining 23% of patients were assumed to switch to hydrogel after the 3 Debrisoft pad applications.
5.5 The sponsor's base case included several key assumptions:
the time horizon of the analysis was the time to complete debridement of the wound
all treatments were provided by a district nurse and were based on a wound size of 10 cm × 10 cm
each nurse visit took 15 minutes
the number of nurse visits per application depended on the product and its availability
1 wound was treated per patient.
The following parameters were based on clinical opinion:
The Debrisoft pad and hydrogel were pre-ordered for use in a home setting but were available immediately in a clinic setting. Larvae needed pre-ordering in both settings.
Following treatment with hydrogel, gauze and larvae, an additional nurse appointment was needed to remove them.
5.6 The External Assessment Centre corrected an error in the implementation of the sponsor's model in which 23% of Debrisoft patients switched to hydrogel (see section 5.4) but the Debrisoft costs for these patients were omitted in the original modelling. Results from the corrected model showed that:
For the clinic setting, the total cost of complete debridement per patient was £97 for the Debrisoft pad, £165 for hydrogel, £180 for gauze, and £306 for larvae, a cost saving per patient of £68, £83, and £209 respectively.
For the home setting, the total cost of complete debridement per patient was £189 for Debrisoft, £308 for hydrogel, £330 for gauze and £351 for larvae, a cost saving per patient of £119, £141, and £162 respectively.
5.7 The sponsor explored the uncertainty around the model parameters and the effect this had on the incremental cost of the Debrisoft pad using deterministic sensitivity analysis. The results of the corrected sensitivity analyses showed that the Debrisoft pad remained cost saving for clinic and home visits in all scenarios tested. The key drivers of the cost savings associated with the Debrisoft pad were the fewer nurse visits needed compared with hydrogel and gauze and the cheaper product costs compared with larvae.
5.8 The External Assessment Centre did not consider that all of the assumptions in the sponsor's cost model were appropriate and presented a revised cost model. Key changes were:
the use of bagged, rather than loose larvae
changing the cost of a district nurse to a more accurate hourly rate
increasing the length of a district nurse visit to 22 minutes in the clinic setting and to 40 minutes in the home setting
the cost of wound dressings was removed from visits when the debridement products had to be ordered
using the cheapest option for the cost of hydrogel, gauze and dressings.
5.9 Results from the External Assessment Centre's revised analysis showed increased incremental cost savings for the Debrisoft pad compared with the sponsor's model. In a community clinic setting, cost savings per patient for the Debrisoft pad of £99, £152 and £375 compared with hydrogel, gauze and larvae respectively, were obtained. In a home setting, cost savings per patient for the Debrisoft pad of £211, £288 and £280 compared with hydrogel, gauze and larvae respectively, were obtained. The External Assessment Centre re-ran the sponsor's sensitivity analyses using the revised cost model and the Debrisoft pad remained cost saving in almost all scenarios. The External Assessment Centre noted that the increased cost savings were mainly a result of the longer length of nurse visits and the higher cost of bagged larvae.
5.10 The External Assessment Centre also conducted a threshold analysis to identify the number of Debrisoft pad applications needed to make it more expensive than hydrogel in 2 different scenarios:
switching to hydrogel after a given number of Debrisoft pad applications (applying the stopping rule)
applying the Debrisoft pad until the wound was completely debrided.
In the first scenario, the Debrisoft pad was no longer cost saving in both the home and clinic settings if the wound was not completely debrided after 7 applications and the patient had to be switched to hydrogel. In the second scenario, when the Debrisoft pad alone was used, it was no longer cost saving in the clinic setting if more than 9 applications were needed per patient and in the home setting if more than 10 applications were needed per patient.
5.11 An additional base-case analysis was calculated by the External Assessment Centre based on assumptions that more closely reflect current practice in NHS community settings according to expert advice to the Committee:
For every larvae application, 5 additional nurse visits were included to allow daily visits to assess and redress the wound.
For home visits, the Debrisoft pad and hydrogel would be carried by the nurse and so would be available at the first visit if needed.
5.12 Results from the additional cost modelling indicated that the costs of complete debridement using the Debrisoft pad were estimated to be even more cost saving per patient compared with the use of hydrogel, gauze and bagged larvae in both community clinic and home settings. When used by a nurse in a community clinic, there were cost savings per patient of £99 for the Debrisoft pad compared with hydrogel, £152 compared with gauze and £484 compared with bagged larvae. When used by a nurse in the home, there were cost savings per patient of £222 for the Debrisoft pad compared with hydrogel, £347 compared with gauze and £469 compared with bagged larvae.
5.13 The Committee identified uncertainties in a number of the parameters in the cost analyses presented by the sponsor. The clinical effectiveness data for the products were obtained from 2 clinical trials with different methodologies and in particular the data available for the Debrisoft pad were limited. Many of the key parameters in the model were based on clinical opinion and the Committee was aware of the large variation in practice in wound care. The Committee recognised that the sponsor had tried to address the uncertainties by conducting deterministic sensitivity analyses to explore the robustness of the cost saving.
5.14 The Committee considered the additional analyses carried out by the External Assessment Centre. The Committee heard advice from clinical experts about the scenarios most likely to reflect routine clinical practice in woundcare management in the community. It agreed that the additional cost analysis (see section 5.12) was the most plausible. This model demonstrated cost savings per patient, when complete debridement was achieved, ranging from £99 to £484, depending on the comparator, in a community clinic and from £222 to £469, in the home setting. The Committee noted that although this indicates considerable cost saving for the use of the Debrisoft pad, there are also considerable uncertainties in the model because of the limited data available and the variation in clinical practice. Results from the sensitivity analyses indicated that the cost savings were robust when key parameters were varied. The Committee was also informed by the External Assessment Centre that it had re-run the cost analyses at the increased cost for the Debrisoft pad and that the results did not change substantially.
5.15 The Committee discussed the 'stopping rule' used in the model, which assumes the Debrisoft pad is used for a maximum of 3 applications and then patients are switched to hydrogel. The Committee understood this assumption was based on the limited data available from Bahr et al. (2011) and does not reflect routine clinical practice. It noted that no other switching sequences were considered in the model. Expert advice to the Committee was that for most appropriate wounds the Debrisoft pad would complete debridement in 1 or 2 applications. The Committee noted the results of the threshold analysis conducted by the External Assessment Centre which showed that the Debrisoft pad was no longer cost saving if a wound needed more than 9 applications in the clinic setting or more than 10 applications in a home setting. Based on the clinical evidence and on expert advice, it considered these scenarios to be very unlikely.
5.16 The Committee considered that it was important to note that the cost savings demonstrated in the model do not take into account the type of treated wound. The Committee understood that there is a large variation in wound types, some of which are more suited to different debridement techniques. Expert advice to the Committee was that the Debrisoft pad was not suitable for wounds with black necrotic tissue or hard eschar. The Committee agreed that selection of an appropriate wound was important if the cost savings demonstrated in the model were to be realised.
5.17 The Committee would like to have seen a cost analysis based on time to wound healing, which could have analysed situations that routinely occur in practice when chronic wounds recur and need debriding again. However, it recognised that data were not available to inform such an analysis.
5.18 For the guidance review, the External Assessment Centre revised the cost model parameters to reflect 2018 values (original guidance values given in brackets). Nurse costs were inflated using the 2015/16 pay and price series. The main parameter changes were the unit costs of Debrisoft at £6.55 (£6.19, 10 cm × 10 cm), Hydrogel at £1.41 (£1.02), gauze at £0.42 (£0.39) and bagged larvae at £319 (£295). In addition, analysis was done with the larger Debrisoft pad at £16.38 (13 cm × 20 cm) and Debrisoft Lolly at £5.88. Use of the Debrisoft pad remains cost saving compared with saline and gauze (£292), hydrogel (£213) and larvae (£277) for a 10 cm × 10 cm wound area in the home setting. Larger Debrisoft pads (13 cm × 20 cm) and the Debrisoft Lolly are also cost saving in the home setting compared with saline and gauze, hydrogel and larvae. In the clinic setting, use of Debrisoft is cost saving for all 3 Debrisoft pads when compared with saline and gauze (£154 for 10 cm × 10 cm), hydrogel (£99 for 10 cm × 10 cm) and larvae (£373 for 10 cm × 10 cm). Full details are in the External Assessment Centre cost model update report.