Analysis of Cost-Effectiveness
LBP
REGRESSION
As indicated previously, an economic evaluation was performed from both societal and health care perspectives. When the societal perspective was applied, all costs were included. When the health care perspective was applied, only costs accruing to the formal Dutch health care sector were included.Mean between-group cost differences were calculated for total and disaggregated costs using ordinary least squares regression analyses. Seemingly unrelated regression analyses were conducted to estimate total cost and effect differences (ie, ΔC and ΔE) while adjusting for baseline values and confounders and considering the possible correlation between costs and effects. Variables were considered confounders if they differed considerably at baseline between the groups or changed the regression coefficient by >10%. For effects, the duration of LBP complaints was a confounder. For costs, the confounders were employment status (societal perspective) and the duration of complaints (health care perspective). Incremental cost-effectiveness ratios (ICERs) were calculated by dividing the adjusted differences in total costs by the adjusted differences in effects (ie, ΔC/ΔE). Bias-corrected and accelerated bootstrapping with 5000 replications was used to estimate the uncertainty surrounding the cost differences and ICERs.Uncertainty surrounding the ICERs was graphically illustrated by plotting bootstrapped cost-effect pairs on cost-effectiveness planes. Cost-effectiveness acceptability curves (CEACs) were constructed to indicate the probability of stratified blended physiotherapy being cost-effective in comparison with face-to-face physiotherapy at different values of willingness to pay [