Economic evaluation

This feasibility study will provide data to identify issues conducting an economic evaluation for the full-scale study. The rationale for undertaking an economic evaluation is to evaluate the feasibility of undertaking a prespecified cost-effectiveness economic evaluation in the full-scale study. In Australia, all drugs, and more recently, certain procedures, undergo a cost-effectiveness analysis to determine whether they will be subsidised by the Australian government. This is usually performed from the perspective of the healthcare sector rather than from the societal perspective.⁴³ We will be following these guidelines. In this pilot/feasibility study, we will ascertain the feasibility of obtaining the outcome (including QALYs) and cost data in a valid manner, determine how much outcome and cost data are missing, and obtain estimates of mean and SD of outcomes and costs. The Consolidated Health Economic Evaluation Reporting Standards (CHEERS)⁴¹ statement checklist will also be followed to report the economic evaluation component in the full study.

In this pilot/feasibility study, all participants in all study arms have concomitant usual care therapy as directed by the treating physician(s) with analgesics, NSAIDS, pregabalin and physical therapies. Arm 4, the control arm, therefore is the usual care arm. In this pilot/feasibility study, the perspective of the health sector is undertaken using intention to treat. The incremental cost per point on the ODI or QALY (based on EQ-5D-5L) will be estimated as the ratio of the difference in average cost and ODI or QALY between intervention arms for three comparisons: (1) epidural steroid versus control, (2) oral steroid versus control and (3) epidural steroid versus oral steroid. Missing data will be imputed with iterative Markov chain Monte Carlo methods. Sensitivity analyses will be performed by converting the SF-36 to SF-6D QALYs to compare QALYs, as well as other sensitivity analyses as recommended by CHEERS.