Cost-utility of a biofilm-disrupting gel versus standard of care in chronic wounds: a Markov microsimulation model based on a randomised controlled trial
Analyse the cost-effectiveness and treatment outcomes of debridement (standard of care) plus BlastX, a biofilm-disrupting wound gel (group 1) or a triple-antibiotic, maximum-strength ointment (group 2), comparing a subset of patients who had not healed at four weeks using the ointment crossed-over to the biofilm-disrupting gel (group 3).
A series of Markov microsimulation models were built using health states of an unhealed non-infected ulcer, healed ulcer, and infected non-healed ulcer and absorbing states of dead or amputation. All patients started with unhealed non-infected ulcers at cycle 0. Complications and healing rates were based on a randomised controlled trial (RCT). Costs were incurred by patients for procedures at outpatient wound care clinics and hospitals (if complications occurred) and were in the form of Medicare allowable charges. Quality-adjusted life years (QALYs) were computed using literature utility values. Incremental cost-effectiveness ratios (ICERs) were calculated for group 1 versus group 2, and group 3 versus group 2. One-way, multi-way and probabilistic sensitivity analysis (PSA) was conducted.
After one year, the base case ICER was $8794 per QALY for group 1 versus group 2, and $21,566 per QALY for group 3 versus group 2. Product cost and amputation rates had the most influence in one-way sensitivity analysis. PSA showed that the majority of costs were higher for group 1 but effectiveness values were always higher than for group 2. Average product use of 3.1ml per application represented 9.4% of the total group 1 cost (average $24.52 per application/$822.50 per group 1 patient). The biofilm-disrupting gel group performed substantially better than the current cost-effectiveness benchmarks, $8794 versus $50,000, respectively. Furthermore, when biofilm-disrupting gel treatment was delayed, as in group 3, the ICER outcomes were less substantial but it did remain cost-effective, suggesting the added benefits of immediate use of biofilm-disrupting gel. Also, when product cost assumptions used in the study were halved (Wolcott study usage), the model indicates important reductions in ICER to $966/QALY when comparing group 1 with group 2. It should be noted that product cost can hypothetically be affected not only by direct product purchase costs, but also by application intervals and technique. This suggests additional opportunities exist to optimise these parameters, maximising wound healing efficacy while providing significant cost savings to the payer.
The addition of the biofilm-disrupting gel treatment to standard of care is likely to be cost-effective in the treatment of chronic wounds but when delayed by as little as 9–12 weeks the ICER is still far less than current cost-effectiveness benchmarks. The implication for payers and decision-makers is that biofilm-disrupting gel should be used as a first-line therapy at the first clinic visit rather than waiting as it substantially decreases cost-utility.
Acute wounds progress through several phases to final healing. When factors interfere with this orderly progression, this causes healing to stop and the wound to become chronic,1 and one of the most common factors for this is biofilm. Unlike planktonic bacteria, which exists as independent cells, biofilm is composed of microorganism aggregates protected by a non-crystalline extracellular matrix (ECM), extracellular polymeric substances (EPS), which is made of proteins, polysaccharides, lipids and other macromolecules.2,3,4,5
Biofilms frequently present without overt clinical symptoms of infection, are difficult to visualise except through imaging techniques due to their depth, and hard to eradicate by antibiotics because the tough EPS encapsulation makes penetration difficult. Moreover, with time, biofilm can adapt and evolve with cooperation of different species (quorum sensing), which provides further protection of bacteria from antibiotics and host defences. That said, the most important characteristics in wound healing impediment are the biofilm's virulence and pathogenicity,6 which may be dependent on the prevalence of less common species and their ability to form polymicrobial colonies.7,8,9
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