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Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - May 2019)
Spondyloarthritis (SpA) is an inflammatory disease comprising both ankylosing spondylitis and non-radiographic axial SpA. This thesis conducted four studies using data from DESIR, a longitudinal cohort of 708 French SpA patients, focusing on economic questions in the context of SpA treatment recommendations. The objectives of study 1 were to value health resource use and productivity loss among DESIR patients and identify factors associated with costs. Cost valuation was done using public data and factors associated with costs were identified in multivariate regression models. This study showed that anti-TNF agents were the greatest cost driver in DESIR and generated the cost outcomes necessary to perform economic evaluations using DESIR data. The objective of study 2 was to collaborate with rheumatologists to develop measurable definitions of adherence to SpA treatment recommendations. A Delphi survey was conducted with 15 rheumatologists, who developed measurable definitions for 6/11 recommendations. The study uncovered differences of opinion between rheumatologists and generated the classification system necessary to explore adherence to recommendations among DESIR patients. The objective of study 3 was to examine the effect of adherence to anti-TNF use recommendations on outcomes in DESIR. Employing alternate definitions of adherence, patients were classed as adherent anti-TNF users, non-adherent anti-TNF users, adherent non-users, and non-adherent non-users. Following one potential definition, non-adherent anti-TNF users had significantly increased non-biologic costs compared to adherent users, while non-adherent non-users had significantly worse health outcomes than adherent anti-TNF users. This study showed that the impact of adherence to anti-TNF recommendations is sensitive to the definition of adherence and highlighted the need to validate methods to measure adherence. The objective of study 4 was to explore whether the French anti-TNF access restrictions are the most cost-effective in that setting relative to other potential restrictions. Five separate datasets were created comprising DESIR patients satisfying different sets of anti-TNF access criteria. Incremental cost-effectiveness ratios (ICERs) associated with anti-TNF use were calculated in each subset in basecase and sensitivity analyses. A sensitivity analysis simulating a 24-week stopping rule among anti-TNF non-responders demonstrated the effect of non-response on anti-TNF cost-effectiveness. The study underscored the need for evidence-informed anti-TNF access restrictions.
Traditionally, productivity loss has been measured according to illness-related absence from work (absenteeism) only. However, there is increasing evidence that presenteeism (reduced intensity and/or quality of labour input) is an even greater source of productivity losses. In addition to empirical measurement issues, there are theoretical issues with regard to productivity valuation. The traditional human capital method assumes that the value of productivity loss to society should be measured as the present values of lost time according to the wage, which is supposed to be equal to the marginal productivity of labour in a competitive labour market. The alternative, friction cost method, is based on the same assumption except that it adjusts for unemployment. However, these methods ignore the effects of risk aversion and team production which cause the wage to be lower than the marginal productivity. Existing productivity questionnaires did not capture sufficient information to enable the proper measurement and valuation of productivity loss from a societal perspective. A new questionnaire, Valuation of Lost Productivity (VOLP), was developed to capture all the time input loss components(absenteeism, presenteeism, employment status changes, and unpaid work productivity loss) as well as information on job and workplace characteristics, based on which wage multipliers can be calculated to value the productivity loss attributable to the reduced time input of workers. The thesis provides evidence for the validity of the VOLP in measuring time input loss due to poor health and its feasibility in evaluating the treatment effect on productivity in people with rheumatoid arthritis. The equality between wage and marginal productivity was tested using the Workplace and Employ Survey, a linked employer-employee database in Canada. Some evidence suggests that team workers are underpaid compared with their relatively higher iii productivity. In small firms, higher absenteeism results in lower productivity and wage, and the marginal productivity loss with respect to team worker absenteeism is higher than the wage loss. Furthermore, for team workers, health-related frequent reduction at work results in lower productivity and the resulted productivity loss is more than the wage differentials.