Aggregate distributional cost-effectiveness analysis of biologics for the treatment of ankylosing spondylitis in Chile

Background and Objective Ankylosing spondylitis is a complex rheumatic disease, characterised by chronic and progressive inflammation of the spine, causing an important health and economic burden for the person with the condition. Evidence shows the unequal impact of the disease in different groups of people, with a higher burden for lower socioeconomic groups. The objective of this study is to evaluate the impact of the use of biologics for the treatment of ankylosing spondylitis on health inequities in Chile. Methods We conducted an aggregate distributional cost-effectiveness analysis. Data on health outcomes and costs were derived from a cost-effectiveness model of secukinumab, etanercept, certolizumab pegol, infliximab, adalimumab and golimumab versus treatment as usual for the treatment of ankylosing spondylitis from the Chilean healthcare system perspective. Health gains and health opportunity costs were distributed across socioeconomic subgroups. Health and equity impacts, measured using the Atkinson index, were assessed on an equity-efficiency impact plane. Results All treatments had a positive impact on equity relative to treatment as usual. At an opportunity cost threshold of 1 Gross Domestic Product per capita/quality-adjusted life-year, secukinumab improved societal welfare irrespective of the Atkinson index value. When varying thresholds (2 and 3 Gross Domestic Product), all assessed technologies contributed to an increase in societal welfare, regardless of the Atkinson index. Conclusions Biologic treatment for ankylosing spondylitis, such as secukinumab, may reduce health inequity in the Chilean population. An aggregate distributional cost-effectiveness analysis framework is feasible to implement alongside a cost-effectiveness analysis in the context of the Chilean healthcare system to provide additional information of equity impacts for health technology assessment recommendations and policy making.