To carry out a pilot study to demonstrate the feasibility of the contingent valuation (CV) approach to identify net benefits gained from spinal interventions; and to conduct a formal cost-benefit analysis (CBA) using a retrospective study design. The study design is a CBA feasibility study using a CV survey with ex post willingness-to-pay/willingness-to-accept (WTP/WTA) questions. The CBA study was carried out in the specialty of spinal surgery.
Although increasing data are gathered on the societal costs of low back pain, little information is available on how patients “value” the benefits of surgery or whether interventions in this area are indeed cost-beneficial. CV surveys are used in CBA to elicit the consumer's monetary valuations for program benefits.
A total of 115 patients after lumbar fusion, discectomy, or decompression were asked to respond to an ex post questionnaire on their WTP/WTA for their respective intervention. Additional questions addressed socio-demographics, household income, and clinical outcome. WTP/WTA was related to the actual intervention costs and clinical outcome. The WTP and cost data were then combined within a formal CBA framework with associated 95% confidence intervals generated using bootstrapping methods.
The response rate was 91.3% (n = 105). 89.5% were satisfied/very satisfied with the treatment. 76.2% found the result of the operation was good/excellent and 75.7% would choose the operation for a given hypothetical intervention cost. Mean stated WTP was 20% lower than the actual operation costs (not known to respondents) for spinal fusion, although it was 37% higher for discectomy and 10% higher for decompression. The individuals' financial situation was the strongest predictor for WTP. Pain improvement, present pain, duration of hospitalization, and estimated intervention costs were significant independent predictors in the expected direction for the WTP, having controlled for socio-demographic and financial confounding variables.
This study explored the feasibility of the CV approach for spinal interventions. The approach produced results suggesting positive net benefits with their associated levels of variability for discectomy and decompression, indicating that such surgery is cost-beneficial within a CBA framework, but this conclusion is not supported in the case of spinal fusion. Nevertheless, to improve reliability of the net-benefit estimates for these interventions, we recommend further studies comparing in particular ex ante and ex post WTP methods.