Compared with Brazilians with ankylosing spondylitis (AS), individuals from Quebec with AS show greater medication persistence and less socioeconomic disparity related to persistence, according to study results recently published in Current Medical Research and Opinion.

This study included individuals with AS who received antitumor necrosis factor (anti-TNF) and/or conventional disease-modifying antirheumatic drugs (cDMARDs) from Quebec (anti-TNF±cDMARD, n=983; cDMARD only, n=2660) and Brazil (anti-TNF±cDMARD, n=15,481; cDMARD only, n=3838). All health administrative data were collected between 2010 and 2015. Discontinuation of therapy was defined as a 60-day gap in cDMARD supply or a switch from one anti-TNF drug to another. Medication persistence was assessed at 1 and 2 years after cohort entry date. To identify potential associations with therapy continuation at 1 and 2 years in the anti-TNF and cDMARD groups, multivariable Cox proportional hazards models were used. 

One-year persistence was lower for individuals in Brazil than in Quebec in both the anti-TNF (62.1% vs 66.9%, respectively) and cDMARD (30.7% vs 67.0%, respectively) groups. At the end of year 2, persistence rates declined in both Brazil and Quebec in anti-TNF (47.9% vs 51.5%, respectively) and cDMARD (18.1% vs 53.5%) groups, though individuals from Quebec still had better persistence rates. Multivariate Cox regression analyses at both 1 and 2 years revealed associations of discontinuation rates with sex, age, and comorbidities.

Brazilians residing in areas with a higher municipal Gini index and lower Human Development Index were at greater risk for discontinuation, though persistence did not vary among individuals from Quebec by socioeconomic status or rural/urban residence.

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Study limitations included lack of data on disease severity, clinical measures, and reasons for treatment discontinuation; the potential for residual confounding bias; and a lack of evaluation on persistence among anti-TNF switchers.

Study researchers concluded, “Canadian AS patients from Quebec showed better rates of medication persistence than Brazilian patients, in both 1-year and 2-years of follow-up.” Furthermore, “age, sex, and comorbidities had a significant influence on medication persistence in both countries.” They added, “While medication persistence in Quebec did not seem to differ between geographical regions or socioeconomic status, in Brazil, we found some differences associated with these characteristics, which may be related to inequities in the access to [healthcare].”

Reference

Acurcio FA, Guerra Junior AA, da Silva MRR, et al. Comparative persistence of anti-tumor necrosis factor therapy in ankylosing spondylitis patients: a multicenter international study [published online February 11, 2020]. Curr Med Res Opin. doi:10.1080/03007995.2020.1722945