Comparative persistence of anti-tumor necrosis factor therapy in ankylosing spondylitis patients: a multicenter international study

Objective. To evaluate persistence on conventional DMARDs (cDMARDs) and anti-TNF therapies, and to identify potential determinants of discontinuation among individuals with ankylosing spondylitis(AS) living in Brazil and Quebec, Canada.
Methods. We conducted a cohort study of AS patients using health administrative data (2010-2015). One-year and 2-year persistence rates were assessed. Cox regression was used to identify potential determinants of therapy discontinuation.
Results. One-year persistence was less likely in Brazil for both anti-TNF and cDMARDs (Brazil: 62.1% and 30.7%, Quebec: 66.9% and 67.0%). The 2-year persistence rates were lower for both anti-TNF and cDMARD, but remained higher in Quebec (Brazil: 47.9% and 18.1%, Quebec: 51.5% and 53.5%). In multivariate Cox regression analysis, age, sex and comorbidities were associated with persistence in both countries. In Quebec, persistence did not differ between rural and urban regions or with socioeconomic status. While in Brazil, patients in regions with higher Human Development Index and those in cities with lower Gini index were less likely to discontinue therapy.
Conclusions. Canadian AS patients were more likely to persist on therapy compared to Brazilian patients, although rates were lower at 2 years in both countries. Socioeconomic disparity in persistence was found in Brazil, but not in Quebec.