Modelling the cost effectiveness of treatments for Parkinson's disease: a methodological review.

The objective of this review was to assess models of cost effectiveness for Parkinson's disease (PD) published after July 2002 and to derive recommendations for future modelling. A systematic literature search was performed in the databases PubMed, Current Contents, EMBASE, EconLit, the Cochrane Database of Systematic Reviews, and DARE (Database of Abstracts of Reviews of Effectiveness), NHS EED (Economic Evaluation Database) and HTA (Health Technology Assessment) of the UK NHS Centre for Review and Dissemination (July 2002 to March 2010). Only fully published studies using decision trees, Markov models, individual simulation models or sets of mathematical equations were included. Most of the 11 studies identified used Markov models (n = 9) and two employed were based on decision trees. Based on the Hoehn & Yahr (HY) scale, authors evaluated the cost effectiveness of drug treatments (n = 6), surgical approaches such as deep brain stimulation (n = 1) or striatal cell grafting (n = 1), and diagnostic procedures such as single photon emission computed tomography (SPECT) testing (n = 3) over a time horizon of 1 year to lifetime. Costs were adapted to address a societal and/or healthcare provider/third-party payer perspective. All but one of the interventions investigated were considered cost effective or cost saving. Cost-effectiveness modelling in PD between 2003 and 2010 showed only minor improvement when compared with our earlier review of models published from 1998 up to 2003. Cost-effectiveness modelling recommendations were complied with to only a limited extent, leaving room for quality improvement. More advanced modelling approaches may, so far, be under-represented, but may be used in the future, driven by the research question. Adverse events of treatment, co-morbidities or disease complications are not yet sufficiently included in the models to adequately represent clinical reality.