Statistical analyses
APPENDIX
Descriptive statistics were used to summarize and compare the baseline characteristics of the patients in the control- and intervention groups. The main statistical analysis for estimating treatment effects was performed with an intention-to-treat approach using all available data and a 3-level linear mixed model with random intercepts for the cluster (center) and patient (repeated measures), and with treatment group, baseline values, seasonal and calendar time treated as covariates. This method provided the estimated mean outcome level at each measurement time point, and the results of the group comparisons were reported as mean differences [intervention minus control] with 95% confidence intervals (CIs). Dropout analyses were performed to determine the response rate and attrition, and to explore the characteristics of completers and dropouts. The significance level was set at 0.05. Analyses were conducted in Stata IC16.Several sensitivity analyses were conducted to investigate the robustness of our findings and the influence of missing data. These included within-cluster comparisons of the control- and intervention group, unadjusted intention-to-treat-analyses of the total sample using all available data, and rigorous per-protocol analyses. The per-protocol population was defined based on information from the fidelity checklist combined with patient-reported data on whether follow-up was needed and planned at discharge, and received within 7 months after rehabilitation (Appendix Table 2). To be included in the per-protocol analyses, a patient was required to fulfill 16 out of 19 protocol components, in addition to having contributed with data on the primary outcome.Additionally, descriptive statistics were used to examine which components of the BRIDGE-intervention were received or not (yes/no) in the sub-group of patients who did not receive the BRIDGE-intervention as intended (the non-per protocol population). Further, we compared the control- and intervention group (total sample) with respect to patient-reported received follow-up (yes/no) in primary healthcare at 2 and 7 months after rehabilitation by using Pearson's Chi-square test.