*3.2. Economic Results*

### 3.2.1. Base Case Analyses

A 33% reduction from the Henriksen et al. meta-analysis was used in the budget impact analysis (OR: 0.67; 0.46–0.98; *p* = 0.04), as established from the results of the literature review [28]. We considered that when the incidence of an outcome of interest was common (>10%), the adjusted OR that was derived from the logistic regression could no longer approximate the risk ratio. We therefore approximated a risk ratio from an adjusted OR ratio and derived an estimate of an SSI reduction that better represented the true RR [43]. The obtained RR (95% CI) was 0.70 (0.49–0.98), and, accordingly, a 30% SSI reduction for TCS introduction was used in the model.

The budget impact analysis estimated an additional annual cost of €600 for a complete conversion of CS to TCS. TCS reduced the number of SSIs by 30%, which led to the avoidance of 3.2 SSIs—over 100 surgeries performed—and associated hospital resources totaling €15,385 (€13,230 for additional LOS and €2155 for additional resource use). The use of TCS resulted in an overall annual net saving of €14,785. The additional €600 associated with using TCS compared with CS were o ffset by the SSI reduction. The model also calculated the minimal SSI reduction required to cancel out the incremental cost of TCS: The additional cost of €600 for advancing wound closure technology was o ffset by an SSI reduction rate of approximately 1.2%, equaling less than a single avoided SSI (0.1 episodes).

### 3.2.2. Scenario and Sensitivity Analyses

When assuming an SSI reduction rate of 2%, the economic model resulted in an overall annual net saving of €426. In this scenario, 0.2 SSI episodes were avoided, thus accounting for a saving of €1026. The incremental expenditure of €600 was o ffset by the SSI reduction risk. Conversely, when the SSI reduction was set at 51%, the annual net saving for the hospital was €25,554 with 5.4 SSI avoided episodes accounting for €26,154 of hospital resources.

The results of the one-way sensitivity analysis, represented as a tornado chart, are presented in Figure 1. The variables with the greatest influence on the annual savings in the model were related to efficacy parameters (SSI risk reduction and baseline SSI rate), with other parameters that were related to cost events found to demonstrate a minor influence on the annual savings. The annual savings remained positive across a broad variation in the ranges for each parameter.

**Figure 1.** Tornado diagram with one-way sensitivity analysis results. Abbreviations: SSI, surgical site infection.

The results of 1000 Monte-Carlo simulations of the annual savings are presented in Figure 2, and the number of avoided SSIs, based on PSA, are presented in Figure 3. The analysis demonstrated that the reduction of SSI episodes due to TCS ranged between 1 and 6 cases in 90% of the simulations. The mean (interquartile range (IQR)) annual savings that were obtained from the PSA was €13,935 (9068–18,665). The whiskers extended the IQR by 1.5 to a maximum of €32,369 and a minimum of −€4987. The analysis demonstrated a 98% probability of TCS being cost saving, based on the assumptions made.

**Figure 2.** Histogram of the number of avoided SSI episodes according the probabilistic sensitivity analysis. Abbreviations: SSI, surgical site infection.
