Challenges in analysis and interpretation of cost data in vascular surgery
Received 31 May 2009; accepted 8 August 2009. published online 05 November 2009.
Objective
Health economic arguments have become increasingly important in clinical decision making, especially when new treatment modalities are introduced. This study reviews the methods used in health economic reports of abdominal aortic aneurysm (AAA) repair and uses original cost data to study how different methods affect interpretation of results in terms of cost differences and economic efficiency.
Design
Publications referenced in PubMed from 2003 to 2008 studying cost of AAA repair were reviewed. Original population-based cost data of AAA repair were analyzed, comparing open (OR) and endovascular repair (EVAR). Means, medians, and cost distributions were calculated, and differences were analyzed with four different statistical methods.
Results
The review showed a mixture of statistical methods used in AAA treatment cost-comparison studies. Presentation of cost data and inclusion criteria varied between studies. The analysis of original data showed skewed distribution of cost data, with large differences between mean and median cost. Although mean values indicated a lower total, perioperative, and postoperative cost for EVAR, the median values indicated OR was the least costly method. Exclusion of extreme values lowered mean perioperative cost of OR by 10%, while cost of EVAR was unaffected. Inferential testing of cost differences by means of four statistical methods showed that P values were highly dependent on test methodology.
Conclusions
Conclusions of health economic reports can be highly dependent on how the data are presented and the statistical methods that are used. We recommend that cost data be presented as mean values with distributions. Exclusion of outliers and focus on P values should be avoided.
aDepartment of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden
bMedical Management Centre, Karolinska Institutet, Stockholm, Sweden
cDivision of Cancer Studies, King's College, London
Correspondence: Dr Kevin Mani, Department of Surgical Sciences, Section of Vascular Surgery, Uppsala University Hospital, SE-751 85 Uppsala, Sweden
Financial support was received by the Swedish Heart and Lung Foundation, the Selander Foundation, the Sigurd and Elsa Golje Foundation, and the Royal Society of Arts and Sciences of Uppsala.
Competition of interest: none.
The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a competition of interest.
ABSTRACT