Sensitivity Analysis
LBP
The direction and magnitude of the differences in costs and effects between the stratified blended physiotherapy group and the face-to-face physiotherapy group as estimated in the sensitivity analyses were not completely in line with those estimated in the main analysis. In particular, when analyzing complete cases only (sensitivity analysis 1), cost differences between the stratified blended physiotherapy group and the face-to-face physiotherapy group were found to be in favor of the stratified blended physiotherapy group, whereas when missing values were imputed (main analysis), these cost differences were in favor of the face-to-face physiotherapy group. This resulted in slightly different CEACs than those obtained in the main analysis and showed that, in the complete-case analysis, stratified blended physiotherapy was dominant over face-to-face physiotherapy. The results of sensitivity analysis 3 showed that, for both perspectives, the cost difference between the stratified blended physiotherapy group and the face-to-face physiotherapy group increased with a higher risk of developing persistent LBP; that is, for the low-, medium-, and high-risk groups, the differences in costs from the societal perspective (QALYs) were €46 (US $49), €1124 (US $1187), and €5225 (US $5520), respectively. For the low-, medium-, and high-risk groups, the differences in costs from the health care perspective (QALYs) were –€21 (US –$22), €101 (US $107), and €425 (US $449), respectively. In line with the main analysis, from the societal perspective, stratified blended physiotherapy did not seem to be cost-effective for the different risk groups for developing persistent LBP (