Tumour necrosis factor inhibitor tapering in patients with ankylosing spondylitis at low disease activity: factors associated with flare

BACKGROUND: To investigate factors associated with flare in patients with ankylosing spondylitis (AS) who tapered tumour necrosis factor inhibitors (TNFis) after achievement of low disease activity (LDA) with the standard dose of TNFis. METHODS: This retrospective cohort study included 101 patients with AS who tapered their first TNFis after achievement of LDA. The proportion of reduced versus standard doses of TNFi throughout the follow up in each patient was quantified using the time-averaged dose quotient (DQ). Clinical characteristics were compared between patients who did and did not experience flare after TNFi tapering. Multivariable Cox regression analysis was performed to identify factors associated with flare. Receiver operating characteristic curve analysis was performed to determine the cut-offs of these covariates that best predicted flare. RESULTS: Of the total 101 patients, 45 (44.6%) patients experienced flare after TNFi tapering. Compared with patients who did not experience flare, those who experienced flare had a shorter disease duration (p = 0.006), shorter LDA duration before TNFi tapering (p < 0.001) and lower time-averaged DQ (p < 0.001). In multivariable Cox regression analysis, the LDA duration [adjusted hazard ratio (HR): 0.944, 95% confidence interval (CI): 0.906–0.983, p = 0.006] and time-averaged DQ (adjusted HR: 0.978, 95% CI: 0.959–0.998, p = 0.032) were inversely associated with flare. The cut-off values of the LDA duration and time-averaged DQ that best predicted flares were <5.3 months and <60.6%, respectively. CONCLUSION: Shorter LDA duration (cut-off value: 5.3 months) and lower time-averaged DQ (cut-off value: 60.6%) were associated with a higher risk of flare after tapering TNFi.