ObjectivePatients with axial spondyloarthritis (axSpA) in clinical remission tapered Tumor Necrosis Factor inhibitor (TNFi) therapy according to a clinical guideline. During 2-years' follow-up, we aimed to investigate flare frequency, dose at which flare occurred, type of flare and predictors thereof.MethodsPatients in clinical remission (Bath ankylosing spondylitis disease activity index (BASDAI)<40, physician global score<40 and without disease activity the previous year) tapered TNFi to 2/3 standard dose at baseline, 1/2 at week (w) 16, 1/3 at w32 and discontinuationed at w48. Flare was defined as: BASDAI flare (BASDAI≥40 and Δ≥20) and/or clinical flare (development of inflammatory back pain, musculoskeletal or extra-articular manifestations and/or ASDAS-CRP increase ≥0.9) and/or MRI flare (≥2 new/worsened inflammatory lesions).ResultsOf 108 patients, 106 (99%) flared before 2 years: 29 patients (27%) at 2/3 standard dose, 21 (20%) at 1/2 dose, 29 (27%) at 1/3 dose and 27 (25%) after discontinuation. One-hundred-and-five (99%) had clinical flare, 25 (24%) BASDAI flare and 23 (29% of patients with MRI) MRI flare. Forty-one patients (41%) fulfilled the ASAS-definition of clinically important worsening (≥0.9 increase since baseline). Higher baseline physician global score was an independent predictor of flare after tapering to 2/3 (Odds ratio=1.19 (95% Confidence Interval=1.05-1.41);p=0.011). Changes in clinical and/or imaging variables in the 16 weeks prior to tapering did not predict flare.ConclusionAlmost all (99%) axSpA patients in clinical remission flared during tapering to discontinuation, but above half not before receiving 1/3 dose or less. Higher physician global score was an independent predictor of flare.