Methods
A systematic review was conducted looking for cost, cost-effectiveness and cost-benefits studies in SCI. Once all articles had been identified, they were screened and critically appraised by multiple reviewers. This information was used to quickly identify potential method limitations in the individual studies, as well as in the area of comparative economic studies in SCI as a whole. The complete methods description and a brief summary of each study is presented in the rest of this chapter, describing the outcomes used, the primary results, and the methodological strengths and limitations.
Economic Evaluation Studies
The economic search terms used for this systematic review are based on validated search algorithms published previously (Wilczynski et al. 2004). For the Medline database, the search terms “cost-benefit analysis.sh. OR costs.tw. OR cost effective.tw.” produces the best combination of sensitivity (95.7%) and specificity (97.2%) of locating methodologically sound economic publications (Wilczynski et al. 2004). The search terms “cost.tw. OR costs.tw.” used in the EMBASE database produces the optimal combination of sensitivity (96.8%) and specificity (97.6%) for economic articles (McKinlay et al. 2006).
Once all full-text articles were screened, the remaining articles were reviewed by three reviewers (AMc, BB and BC) and critically appraised using the Quality of Health Economic Studies (QHES) checklist developed by Chiou and colleagues (2003) and the Drummond checklist developed by Drummond and colleagues (Drummond et al., 1997). This information was used to quickly identify potential method limitations in the individual studies, as well as in the area of economic evaluations in SCI as a whole.
The QHES is a 16-item checklist that was developed in 2003. The checklist items were selected by consensus from a broader pool of items by a panel of 8 Health Economists. Conjoint analysis methods were used to produce utility values for each of the checklist items in relation to the questionnaire. A total of 98 researchers in the field of Health Economics participated in this analysis. The questionnaire was then validated by comparing the checklist scores of a scientific article to global scores reported by experts (Chiou et al. 2003). In a recent quality assessment of economic evaluation study critical appraisal tools, Langer (2012) observed that the QHES and the economic evaluation checklist produced by the British Medical Journal were the most comprehensive checklists. Among all the checklists reviewed, only the QHES has been validated for construct validity and pre-tested among a group of experts. Further, the QHES is also the only checklist where the items are weighted, allowing for a quality rating.
The Drummond checklist was developed in 1997. According to the Cochrane collaboration this checklist has received more scrutiny than other similar checklists (Higgins & Green, 2011). The Drummond checklist is recommended in Cochrane reviews to critically appraise the methodological quality of full economic evaluations developed in tandem with single effectiveness studies (Higgins & Green, 2011).
A brief summary of each study will be presented, describing the outcomes used, the primary results, and the methodological strengths and limitations. Due to the variability in methods, disease population, cohort country of origin and interventions, only descriptive results are reported.
Cost of Illness Studies
The search terms used to identify cost of illness studies differed from those used for cost effectiveness studies. For the Medline database search terms “exp “costs and cost analysis” OR costs.tw. OR cost.tw.” was used. This algorithm had a sensitivity of 95% and a specificity of 95.6% (Wilczynski et al. 2004). The search algorithm “cost.mp. OR costs.tw. OR health care costs.sh.” was used for the EMBASE search and has a sensitivity of 96.8% and specificity of 97.6%.
There is currently no formal tool or checklist for the critical appraisal of the quality of cost of illness studies. Therefore, for this analysis, a modified version of a checklist presented by Larg and Moss (2011) in a critical analysis of cost of illness studies was used. This checklist focused on three major areas: 1) Analytical framework of the study, 2) Methodology and data collection, and 3) Cost analysis and reporting.
Similar to the review of cost effectiveness studies, a brief summary of each study will be reported. Costs were converted to 2018 US dollars by converting currency through the Organisation for Economic Co-operation and Development (2014) reported purchasing price parity and then inflating the cost to 2018 values through United States consumer price index for medical care (United States Department of Labour 2014).
