Efficacy and cost-effectiveness of extracorporeal shock wave lithotripsy for solitary lower pole renal calculi May D J, Chandhoke P S Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology Extracorporeal shock wave lithotripsy monotherapy (ESWL) and percutaneous nephrolithotomy (PN) for the management of lower pole renal calculi. Type of intervention Treatment. Economic study type Cost-effectiveness analysis. Study population Patients with solitary lower pole renal calculi. Setting Hospital setting. The study was carried out at the Kidney Stone Center in Denver, Colorado, USA. Dates to which data relate The ESWL efficacy data related to the period July 1993 to May 1994. Efficacy data for PN were retrieved from a study previously published in 1994. The price year was not stated. Source of effectiveness data Effectiveness data were derived from a single study and a review of previously published studies. Link between effectiveness and cost data This section applies only to the study concerning the efficacy of ESWL. The costing was undertaken on the same patient sample as that used in the effectiveness study and was carried out prospectively alongside the effectiveness study. Study sample 149 patients underwent ESWL on a modified Dornier HM3 under general anaesthesia. The patients were selected retrospectively. No power calculations were reported. Cases of proximal ureteral or uretropelvic junction stones that were pushed into the lower pole of the kidney were excluded from the study. Study design Page: 1 / 5
Retrospective case-series.114 patients were available for follow-up (76%). The follow-up period extended over 3 months. Analysis of effectiveness The primary health outcomes used were the stone-free rate stratified for the size of the stones, the number of patients who required secondary procedures, and the complication rate. Effectiveness results 63 patients had a 76% stone-free rate for stones less than 10 mm.45 patients had a 74% stone-free rate for stones between 11 and 20 mm. 6 patients had a 33% stone-free rate for stones greater than 20 mm. 6 patients required secondary procedures. No patients required hospital admission for septic or bleeding complications. Clinical conclusions ESWL is highly effective for stones less than 20 mm. Modelling A decision analysis model was constructed to carry out the cost-effectiveness comparison. The main feature of the model was the clinical circumstance that once primary therapy (either ESWL or PN) fails, the patient undergoes PN as secondary therapy which is assumed to be completely successful. Outcomes assessed in the review The outcome measures included the stone-free rate, length of stay, and complications. Study designs and other criteria for inclusion in the review Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included Two studies were included in the review. Methods of combining primary studies Investigation of differences between primary studies Page: 2 / 5
Results of the review Stone-free rates for stones less than 10 mm were 74% for ESWL and 100% for PN. Stone-free rates for stones between 11 and 20 mm were 56% and 89% for ESWL and PN, respectively. Stone-free rates for stones greater than 20 mm were 33% for ESWL and 94% for PN. Patients stayed in hospital for 5.3 days on average. Measure of benefits used in the economic analysis The measure of benefits used in the economic analysis was the 3-month post-treatment, stone-free rate. Direct costs Details of which costs were included in the treatment cost measure were not provided. Quantities and costs were not reported separately. The quantity/cost boundary adopted was that of the hospital. The estimation of quantities and costs was based on actual data. Discounting was not relevant given the short study period. Treatment costs for ESWL were obtained from billing charges at the Kidney Stone Center, the average billing charges of 10 consecutive patients undergoing PN at University Hospital during the same period being used to estimate those charges. The price year was not stated. Statistical analysis of costs No statistical analysis was carried out. Indirect Costs No indirect costs were included. Currency US dollars ($). Sensitivity analysis A sensitivity analysis was carried out on the cost and effectiveness of ESWL and PN. Sensitivity analysis was performed with a range of possible costs, having an upper limit of $26,622. Estimated benefits used in the economic analysis Stone-free rates for stones less than 10 mm were 76% for ESWL and 100% for PN. Stone-free rates for stones between 11 and 20 mm were 74% and 89% for ESWL and PN, respectively. Stone-free rates for stones greater than 20 mm were 33% for ESWL and 94% for PN. Cost results The average cost of a single ESWL was $8,213 and a single PN was $26,622 (range: $14,654 - $61,664), for a variety of stone sizes and stone location. Synthesis of costs and benefits Costs and benefits were not combined. For stone size less than 1 cm and between 1 and 2 cm, the PN cost under which it becomes more cost-effective was $11,099 and $12,258, respectively. For stones greater than 2 cm, PN was more costeffective as long as costs remained less than $21,059. Authors' conclusions Page: 3 / 5
ESWL followed by PN for failed cases is more cost-effective if the stone size is less than 2 cm. When the stone size exceeds 2cm, PN is likely to be more cost-effective. CRD COMMENTARY - Selection of comparators The rationale for the choice of the two procedures was clear. Validity of estimate of measure of benefit The outcome measures chosen appear to be valid. Alternatively, the authors could have used the concept of small stonefree fragments. The stone-free rates were not stratified according to caliceal anatomy. Validity of estimate of costs The items which make up the treatment cost measure were not reported. The authors used average charges, which do not represent true opportunity costs, and did not report any adjustments to account for this. It is, therefore, impossible to assess the generalisability of the cost results to other settings or countries. Treatment costs for PN were based on a sample of only 10 patients. However, the authors did perform a sensitivity analysis on the PN costs, and this allows the reader to assess the robustness of the results. Other issues No statistical results were reported, and the reader is therefore not in a position to assess whether or not differences between groups reached a significant level. The study design was not reported in detail. Cost-effectiveness ratios for the base case were not reported. The authors concluded that ESWL, followed by PN for failed cases, was more costeffective when the stone size is less than 2 cm. However, cost-effectiveness ratios for the combined ESWL/PN strategy have not been reported. The major benefit of this study is that the authors developed a decision model that allows other researchers to test the cost-effectiveness of the procedures using cost and efficacy data from their own setting. Implications of the study The results should be validated by a randomised controlled trial and the study should be supported by an extensive cost analysis. Source of funding None stated. Bibliographic details May D J, Chandhoke P S. Efficacy and cost-effectiveness of extracorporeal shock wave lithotripsy for solitary lower pole renal calculi. Journal of Urology 1998; 159(1): 24-27 PubMedID 9400429 Other publications of related interest 1. Go P M N Y H, Stolk M F J, Obertop H, Dirksen C, van der Elst D H, Ament A, van Erpecum K J, van Berge Henegouwen G P, Gouma D J. Symptomatic gallbladder stones: cost-effectiveness of treatment with extracorporeal shock-wave lithotripsy, conventional and laparoscopic cholecystectomy. Surgical Endoscopy-Ultrasound & Interventional Techniques 1995;9(1):37-41. 2. Patel M S, Blacklock N J, Rao P N. Economic evaluation of six scenarios for the treatment of stones in the kidney and ureter by surgery or extra-corporeal shock wave lithotripsy. Health Policy 1987;8(2):207-225. Page: 4 / 5
Powered by TCPDF (www.tcpdf.org) 3. MurrayM J, Chandhoke P S, Berman C J, Sankey N E. Outcome of extracorporeal shockwave lithotripsy monotherapy for large renal calculi: effect of stone and collecting system surface areas and cost-effectiveness of treatment. Journal of Endourology 1995;9(1):9-13. 4. Chandhoke P S. Cost-effectivenessof different treatment options for staghorn calculi. Journal of Urology 1996;156:1567. Indexing Status Subject indexing assigned by NLM MeSH Cost-Benefit Analysis; Humans; Kidney Calculi /therapy; Lithotripsy /economics; Sensitivity and Specificity AccessionNumber 21998000066 Date bibliographic record published 30/04/1999 Date abstract record published 30/04/1999 Page: 5 / 5