The cost-effectiveness analysis was based on one clinical study. A three-state Markov model was used to capture the dynamic nature of wound healing and to project the clinical outcomes beyond the end of the trial, assuming constant transition rates. The time horizon was one year. The study perspective was stated to be that of the long-term care facility.
The primary clinical outcomes were the proportions of patients whose wounds were completely debrided at 42 and 84 days. The randomised trial had two phases: up to 42 days, and up to 84 days. This supplied the probabilities for transition from inflammation to proliferation, and from proliferation to epithelialised. It was conducted at a centre for long-term care and included 27 patients with stage three or four pressure ulcers that had 85% or more of necrotic non-viable tissue. Two investigators, who were blind to allocation, measured the outcomes.
Monetary benefit and utility valuations:
Measure of benefit:
The measure of benefit was the number of epithelialised days, which was the expected number of days that the wound was closed, over one year.
The analysis included the costs of nursing time, collagenase ointment, hydrogel dressing, secondary semi-occlusive dressings, wound irrigation, and wound care kits. The resource use estimates came mostly from the trial, but also from the lead clinical investigator and the literature. The costs were reported in US $. The price year was 2012.
Analysis of uncertainty:
One-way sensitivity analyses were conducted on all model parameters, varying most values by ±20%. A scenario was analysed in which the frequency of dressing changes for hydrogel was reduced from daily to once every three days.