A Review on Cost Effectiveness of Negative Pressure Wound Therapy Vs Traditional Dressing In Diabetic Wounds.

A wound is a break or disruption in normal skin tissue. Wounds can range from superficial disruption to deeper structures such as nerves, vessels, muscles and tendon [2]. Proper healing involves a physiological response to tissue injury mediated by a multitude of factors including cytokines, numerous cell types and vascular events [3]. A few factors can impair adequate wound healing including hyperglycemia, a manifestation of diabetes mellitus. The hyperglycemic state encourages biofilm formation with subsequent delayed repair and development of chronic wounds [3]. It is roughly calculated that 25% of all diabetic patients have impaired wound healing and develop a foot ulcer at some point in time [4]. A devastating consequence to this is lower limb amputation, a complication with significant physical, psychosocial and economic costs [5].

Diabetic foot wounds account for almost 50% of all diabetesrelated hospital stays and it is estimated that 10-15% of diabetic patients develop foot ulcers during their lifetime [6]. Timely and proper treatment is needed to alleviate these complications. This includes elevation, appropriate wound care and dressings, antibiotics in case of infection and assessment and correction of the patient’s vascular status. All this is done through the involvement of a multidisciplinary team but primarily depends on patient education and wound care to prevent more critical issues [7,8].

Over the years there has been increasing research into developing new therapies to limit the serious complications and high costs incurred. In 1997, Morykwas et al. [9] put forward a new principle in wound management. They explored VAC following previous experiments with negative pressure dressing where it was found that negative pressure through a suction mechanism drains fluid exudate and increases blood flow to wounds, thus promotes healing [9]. An increased Doppler flow was observed with higher vacuum settings, creating a better wound bed, decreased oedema and increased perfusion of granulation tissue [10].

NPWT has been observed as particularly useful in diabetic wounds as a salvage technique after other treatment options have failed. Benefits of NPWT in diabetic ulcers include reduction in ulcer size, reduction in length of hospital stay, reduction in total costs for diabetic patients and less costs for diabetic wound dressings [1]. In the light of the improvements in healing through NPWT, hospitals around the world have increased their use over the years.

The aim of this review is to analyze the cost effectiveness of NPWT when compared to traditional dressings in diabetic wounds. This review evaluates recent literature relating to cost benefit analysis and assesses the length of hospital stay and quality of life in patients treated with VAC as a secondary outcome.

Table 1 summarizes aim as per PICO framework.

Table 1:Aim as per PICO Framework.

Search Strategy

An online search was conducted on Ovid Medline to address the objective of this literature review. English language literature from 2012 to 2022 was considered. A ten-year period was selected to obtain the most recent results about the topic and cover ongoing studies.

Table 2:Search Results.

Studies retrieved include cost effectiveness and cost utility analysis of NPWT when compared to alternative dressings. One of the cost-effectiveness analyses by Kirsner et al. [11] analyses venous and DFUs but only data relating to diabetic ulcers will be considered for this review.

The Critical Appraisal Skill Programme checklist [12] will be used to evaluate the literature.

The studies considered include:
1. Evaluation of Wound Care and Health-Care Use Costs in Patients with Diabetic Foot Ulcers Treated with Negative Pressure Wound Therapy versus Advanced Moist Wound Therapy by Driver and Blume [1].
2. A Cost-Effectiveness Analysis Comparing Single-use and Traditional Negative Pressure Wound Therapy to Treat Chronic Venous and Diabetic Foot Ulcers by Kirsner et al. [11].
3. Cost-Utility Analysis of Negative Pressure Wound Therapy Compared with Traditional Wound Care in the Treatment of Diabetic Foot Ulcers in Iran by Alipour et al. [13].

The retrospective analysis by Driver and Blume [1] deals with evaluation of wound care and healthcare use costs in patients with DFUs treated with NPWT vs AMWT. Data for this study was acquired from a RCT by Blume et al. [10] whereby three hundred and fortytwo patients were engaged in a multi-centre trial involving two study arms, NPWT or AMWT, for treatment of DFUs until closure or for a maximum of one hundred and twelve days. This initial study evaluated wound care while Driver and Blume et al. [1] study analysed wound management and cost analysis. For this review, only cost analysis will be considered.

The principal finding from this study was that NWPT is more cost effective when compared to AMWT in diabetic wounds mainly due to lower costs on procedures and reduced use of hospital resources.

Table 3 summarizes the aim, methods, results and limitations for this study.

Table 3:Aims, method, results and limitations for Driver and Blume [1].

The aim of the study is detailed and well defined with a primary endpoint of cost analysis and secondary endpoint of clinical analysis. A lot of information is given about the previous study with an explanation of numbers until the end of study. However, the authors fail to mention how the patients were selected from the initial study. This creates a risk for selection bias and reduces reliability.

The study was a multi-centered study. However, power calculation is lacking, thus an increased risk for Type II error is created and it has decreased external validity. A good summary of how cost per patient is calculated is given and this makes the study reproducible in case similar studies are carried out.

The study tackles cost analysis from a different perspective when compared to Kirsner et al. [11] and Alipour et al. [13]. These two studies use the Markov model to compare wound management techniques in diabetic foot and carry out cost-benefit analysis through different strategies (case base and sensitivity analysis) whereas Driver and Blume [1] analyze results by Fisher’s exact test and log-rank test. While Fisher exact test studies the relationship between two categorical variables and the log-rank test evaluates the risk adjusted event rates, a cost benefit analysis would have been more appropriate to analyze expected benefits from each wound dressing in relation to its cost. A sensitivity analysis for instance would have been good enough to analyze how independent variables affect dependent variables and provide a better costbenefit analysis with respect to any additional costs. Besides this, any assumptions regarding cost estimates were not accounted for in data analysis.

Cost for NPWT is consistently lower than AMWT in all scenarios as indicated in Table 3. The fact that wound-related and non-wound related costs are divided provides a distinction where main costs are incurred. A comparison of this study to other studies is carried out namely to the study by Apelqvist et al. [14] and Flack et al. [15]. These studies had similar conclusions to this study increasing reliability of findings and validity.

In conclusion, overall NPWT is more cost-effective when compared to AMWT as it incurs lower cost and decreases hospital resource use. However, there are several potential sources of bias in the study, namely lack of power calculation and limited costbenefit analysis representations. Hence, the study may be graded as 1- according to the Harbour &Miller classification [16].

The retrospective study by Kirsner et al. [11] analyses the cost-effectiveness of SNPWT vs TNPWT to treat chronic venous ulcers and DFUs. The study extrapolated data from a multi-centre perspective RCT of one hundred and sixty-one patients by Kirsner et al. [17] which compared SNPWT and TNPWT for treatment of venous ulcers and diabetic wounds in the United States. This study is a follow up to analyze the cost-effectiveness of SNPWT over TNWPT using a decision analytic model. For this review, only data related to DFUs will be considered. The key finding from this review is that SNPWT is more cost effective than TNWPT. The preferred therapy was found to provide a less economic burden to healthcare policy makers regarding DFUs.

The aim, methods, results and limitations of cost-benefit analysis are summarized in Table 4.

Table 4:Aims, method, results and limitations for Kirsner et al. [11].

The objective of the study is defined as a similar statement similar to the title however no primary or secondary outcomes are indicated. Reference is made to the initial RCT however no details are available with regards to characteristics for patient recruitment and power calculation, increasing risk for bias and decreasing validity and reliability of the study. A strong point of the study is that data was obtained from a multi-centre study, however data analysed is only obtained from one RCT of one hundred sixtyone patients. Although the sample size is large, lack of power calculation increases the risk of Type II error and reduces external validity. Data from only one trial, thus one cost-minimization analysis, may create room for bias mostly in design, recruitment, sample population and data analysis. Despite data from only one RCT, this provides substantial evidence when assessing the cost effectiveness of SNPWT as it is based on updated trial analyzing the clinical effectiveness of this wound therapy. Although it requires several assumptions that might affect the average cost-effectiveness, the authors carried out a probability sensitivity analysis, based on the uncertainty in the parameters of the technique. This confirmed that the results of SNPWT were sensitive to alternative model assumptions.

The results described in the study showed that SNPWT was economically dominant in four analysis - base case analysis, oneway sensitivity analysis, scenario analysis, probabilistic sensitivity analysis. The consistent dominance is namely due to difference incidence of healing and reduced mean duration of SNPWT and TNPWT. SNPWT was also cost-effective when switching treatment. The use of multiple analyses sets makes the results more significant as they remain constant with all analyses. Within sensitivity analysis, the effect of a shorter duration of TNPWT was also studied. In this case SNPWT also remained economically better than the other therapy. This indicates that SNPWT is valid over a multitude of different treatment pathways.

Kirsner et al. [11] make a comparison of SNWPT with other studies that tackle the subject from other points of views other than cost analysis. Hurd et al. [18] suggest that change of dressing time is often shorter in SNPWT when compared to other dressings while Kirsner et al. [17] state that patient satisfaction was higher with SNPWT. These factors indicate that in addition to cost effectiveness, SNPWT also offers overall better patient satisfaction.

The study concludes that SNPWT for lower extremity DFUs is more cost effective than TNPWT. Results showed increased cost savings and a reduction in the total number of open ulcer weeks between 12 and 26 weeks. SNPWT was found to be economically dominant in multiple scenarios and analyses. The study would be graded as 1- according to the Harbour & Miller classification [16] due to significant risk of bias and only one RCT involvement. Further studies with more RCTs and dated economic evaluations are required to improve external validity.

Alipour et al. [13] analyze the cost-utility analysis of NPWT compared with TWC in DFU treatment in Iran. Two hundred patients treated for DFUs in Iran in 2016 over the course of one year were considered with half being treated with TWC and the rest treated by NPWT. A cost utility analysis was performed to assess mortality and morbidity of each type of wound dressing. The main inference was that NPWT is more cost effective than TWC with NPWT at $4668 lower cost per patient per year as opposed to TWC. NPWT also showed a higher QALY index over TWC.

Table 5 summarizes the aim, method, results and limitations of cost-benefit analysis for this study.

Table 5:Aims, method, results and limitations for Alipour et al. [13].

The study comprises data from Iran with no mention of a singlecentre or multi-centre data collection. Although one may assume that data from a whole country is a population base study, the study has no power calculation. The authors do not mention how the sample size was selected, and this increases the risk of Type II error and decreases the study’s external validity. Additionally, no inclusion or exclusion criteria are identified, and selection methods are not declared thus increasing the risk of inconclusive results and decreasing reliability.

Cost benefit analysis is done through base case and sensitivity analysis. The base case analysis collects data regarding one model while the sensitivity analysis accounts for any deviations that results may show due to variable figures. Probabilities relating to transition rates were obtained from Flack et al. [15] and Whitehead et al. [19]. This is useful as using common principles from other studies may increase transferability of information and add external validity.

Results indicate that NPWT is more cost effective when compared to TWC with a v4668 cost difference between the two dressing types over one year per patient. NPWT also had a higher QALY index over TWC. Varying parameters did not change the dominant strategy. Results also showed that NPWT reduces the number of amputations. The results of this study are like Flack et al. (2008) and Whitehead et al. (2011) studies increasing validity of this study. The former identified 0.53 QALY in NPWT patients when compared to 0.52 in TWC patients and a reduction in cost per patient with NPWT of $22004 per year. Whitehead et al. (2011) had similar results with a cost reduction of $4.68 million and 3 more QALY in NPWT patients. Thus, NPWT has a lower cost and greater QALY out of the two dressing types with a reduced effect on morbidity and mortality in diabetic patients.

The authors are aware of the limitations of this study and indicate that the one-year timeframe of this study does not assess long-term effectiveness and lifelong rates of disability and amputation. The analysis lacks data on utility weights, transition probabilities and quality of life indices in Iran. Furthermore, it only presented the provider’s perspective for the cost benefit analysis. A social perspective may be considered in future studies for a better economic evaluation. Given these limitations for this economic evaluation, the study may be classified as 2- according to Harbour & Miller grading system [16] due to the high risk of bias. More multi-centered studies with longer timeframes and a social perspective with regards to cost benefit analysis are required to improve external validity.

The studies relating to cost-effectiveness of NPWT vs alternative dressing in diabetic wounds show that NPWT is cost-effective when compared to the other management strategies [1,11,13]. This is due to a shorter length of stay and lower cost for patients being treated with NPWT, mostly in relation to diabetic wound dressings.

The studies have some common limitations, namely lack of power calculation and high risk of bias giving them a score of 1- or 2- on Harbour & Miller classification [16]. This creates a need for more rigorously conducted studies with greater sample sizes and improved cost benefit analysis. Additionally, study data should be obtained from more than one potential source to improve research validity as much as possible. In summary, the existent data shows good evidence that NPWT is cost effective in management of diabetic patients, but research is limited.

None.

No conflict of interest.

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