2.2.1. Model Inputs

The model included the following inputs: baseline SSI rate, SSI reduction, the additional cost of TCS over CS, the number of sutures used per procedure, and the cost of SSI. The baseline SSI rate was taken from an Italian trial that reported the SSI rate in 281 patients undergoing colorectal resection as

equal to 10.6% [23]. SSI reduction, attributable to implementing TCS into clinical practice, was selected from the reviewed meta-analysis as previously described. The differential cost of sutures was assumed to be an additional €1 for TCS compared with CS. According to expert opinion, six absorbable sutures are required per abdominal procedure, with 600 sutures used when assuming that 100 procedures are performed annually. The cost of a single SSI episode was taken from an Italian study, published in 2000, that evaluated the hospital resources that are consumed to treat postoperative infections among patients with gastrointestinal cancer who underwent abdominal procedures [32]. The cost that was identified for each wound infection was inflated to 2019 costs according to the Italian Institute of Statistics Consumer Price Index of 1.296. An SSI cost—specific for an abdominal surgery and referred to the Italian environment—of €4,838 was therefore considered in this economic analysis. The cost breakdown was attributed to additional resource use (14%) and prolonged length of stay (LOS) (86%), as previously described [32].

### 2.2.2. Scenario and Sensitivity Analyses

To assess the robustness of the primary analysis, scenario and sensitivity analyses were conducted from the Italian hospital perspective (general surgery unit). In the scenario analyses, the model assumed different scenarios from the base case according to the SSI risk reduction: 1) The SSI reduction rate was set at the lower bound of the CI, and 2) the SSI reduction rate was set at the upper bound of the CI. Uncertainties surrounding model parameters were also assessed through one-way sensitivity analyses that varied key parameters by using the 95% CIs where possible or by applying a ± 25% range of variation. The considered parameters included the baseline SSI rate, the cost of a single SSI, the number of sutures used per surgical procedure, and the SSI reduction rate. Furthermore, a probabilistic sensitivity analysis (PSA) was performed in which the above parameters were simultaneously varied by randomly sampling these values from the distribution assigned for each parameter for 1000 iterations. Distributions used for each parameter are presented in Table 1.



Abbreviations: SSI, surgical site infection.
