Statistical analyses
Analyses were performed on an intention-to-treat basis. Qualitative variables were compared using the χThe cost-utility analyses at 30 days and at 3 months were performed on cases with complete QALYs (no missing data). Then, a non-parametric bootstrap method (10,000 replications) was used in order to study the uncertainty associated with the sample and to construct a 95% confidence interval (95% CI) for the ICERs. This was followed by the construction of a Cost-Utility plane (CU-plane) and an acceptability curve from the bootstrap and the 95% CI of the ICERs. This curve is used to represent the probability that the VATS strategy is efficient when compared to the thoracotomy strategy (y-axis) as a function of different possible values of society’s Willingness-To-Pay (WTP) for an additional health unit (x-axis). A sensitivity analysis was performed using multiple imputation by chained equation method in order to take into account patients with missing data [The version 9.4 SAS was used for the analyses. The threshold for significance was set at 0.05.