Background Tumor necrosis factor (TNF) inhibitors is effective in ankylosing spondylitis (AS) management and had been approved by the Bureau of National Health Insurance (NHI) for AS treatment in those with inadequate response to conventional therapies since 1999 in Taiwan. Drug survival was considered a summary measure of treatment success. However, factors associated with anti-TNF discontinuation risk in AS patients were still unknown in Taiwan.
Objectives To investigate factors associated with drug discontinuation in anti-TNF-naïve patients with AS treated with etanercept (ETN) and adalimumab (ADA).
Methods This retrospective nationwide population-based cohort study identified 1401 anti-TNF-naïve AS patients (age at diagnosis ≥16 years) in whom ETN (n=441 or ADA (n=960) was initiated using the 1999–2011 National Health Insurance (NHI) claims data. The outcome was the time to anti-TNF drug discontinuation. We defined drug discontinuation as non-persistence of prescription for more than 84 days. To test the risk of drug discontinuation associated with ADA use, prior medication (within one year before anti-TNF initiation), concomitant medication, baseline demographic data and comorbidity, we calculated adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) using Cox proportional hazard regression analyses. Analyses were also conducted in ETN users and ADA users respectively, and we tested whether the HRs associated with covariates were different between ETN and ADA users.
Results The risks of drug discontinuation were not different between ADA and ETN users (HR, 1.06; 95% CI, 0.84–1.35). In all subjects, prior use of leflunomide or corticosteroid was associated with a higher risk of anti-TNF discontinuation; while concomitant use of methotrexate (MTX) or NSAID was associated with a lower risk of anti-TNF discontinuation. In subgroup analysis, concomitant MTX use was a protective factor of drug discontinuation in ADA users (HR, 0.36; 95% CI, 0.25–0.54), but not in ETN users (HR, 1.32; 95% CI, 0.64–2.72; p for interaction =0.039).
Conclusions Among anti-TNF naïve AS patients, risk of drug discontinuation was not different between ETN and ADA users. Concomitant MTX use was associated with a lower risk of drug discontinuation in ADA users, but not in ETN user.
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Disclosure of Interest None declared
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