Cost-Utility Analysis of Ureteral Stone Management

Introduction

While treatment guidelines for ureteral stone are well established, the decision is often based on the expert opinion and clinical tacit knowledge. Very few studies take the patients’ preference into account and the clinical decision making can make better choice. The aims of this study were to perform meta-analysis of the stone clearance rate of ureteroscopic lithotripsy (URSL) and extracorporeal shock wave lithotripsy (ESWL) by using systemic review, to apply standard gamble method to evaluate the patient preference by utility measurement on every treatment and prevention strategy in ureteral stone management, and finally to use a multi-state disease progressive model to evaluate the cost-effectiveness of every treatment and prevention strategies by deterministic and probabilistic methods.

Materials and Methods

In the literature review, the published studies were divided into randomized control trials and comparative studies according to the study design. The stone clearance rate and relative effectiveness between URSL and ESWL were estimated by the stratification of stone site and size.
The utility values of clinical treatment and prevention conditions were measured by modified standard gamble method. The novel method different from conventional standard gamble method includes setting reference state and ranking the target states. After defining the relative utility values, the absolute utility values (with anchor states of complete health and death) were calculated by chaining transformation method. The modified method may even detect difference between minor clinical conditions. For evaluating the associating factors, the value transformation and linear regression analysis were conducted in this study.
Incorporating the results of literature review and expert opinion retrieved by Delphi method, the disease progressive models for acute and chronic phases were established. The cost-utility analysis with the constructed Markov chain model was performed by using Monte Carlo simulation in TreeAge®. Two levels of uncertainty were taken into account in the current probabilistic approach, the first-order uncertainty for chance variability and the second-order uncertainty for parameter uncertainty. The available treatment and prevention strategies were evaluated to define the most cost-effective decision.

Main Results

1. The meta-analysis revealed the stone clearance rate of ESWL for large, medium, and small stones were 0.303, 0.409, and 0.440 for proximal stones and 0.726, 0.777, and 0.831 for distal ones. The results of URSL for large, medium, and small stones were 0.550, 0.649, and 0.649 for proximal stones and 0.864, 0.893, and 0.931 for distal ones.
2. In a total of 267 cases from urological clinic, 89 were sampled to complete the utility measurement. The utility value of hemodialysis state, as the reference state, was 0.399±0.343. In acute phase condition, the utility values of expected medical treatment (0.935±0.096), ESWL (0.930±0.098), URSL (0.914±0.106), and invasive surgical treatments (0.846±0.165) were measured. The utility value of chronic conditions were also reported: no prevention (0.959±0.090), life style modification (0.974±0.076), regular surveillance (0.971±0.079), and long term medical prophylaxis (0.955±0.088). The associating factors were gender, education level and experience of URSL.
3. For large ureteral stone, the best treatment strategy was the combination of URSL as primary and salvage therapy. For medium stone, the best method was expectant management with URSL as following treatment choice. For small stone, the best strategy was expectant management with applying URSL for residual stones.
4. By the outcome of recursive events, the life style modification, medical prophylaxis and regular surveillance were cost-effective. In considering the willingness to pay as one quarter GNP (NTD 132000), the best choice is life style modification only. However, taking quality-adjusted life time as the outcome parameter, only life style modification was cost-effective.

Conclusion

In this study, a novel modified standard gamble method was develop to evaluate the patient preference to treatment and prevention conditions in ureteral stone management. The result was constructed into the cost-utility analysis. By considering individual utility, we adopted the probabilistic approach in cost-utility analysis to establish the clinical guideline for ureteral stone treatment and prevention.