Severe Symptoms Predict Residual Disease After Transitioning From High to Low Disease Activity in Axial Spondyloarthritis: A Longitudinal Study.

OBJECTIVE To investigate whether very high disease activity (VHDA) status or severe symptoms when in HDA state predict residual disease after achieving inactive disease/low disease activity (ID/LDA) in axial spondyloarthritis (axSpA). METHODS Prospective data from the SpA-Net registry were used. HDA was defined as an Axial Spondyloarthritis Disease Activity Score (ASDAS)≥2.1, and ID/LDA as ASDAS<2.1. VHDA (predictor 1) was defined as ASDAS>3.5, and severe symptoms when in HDA state (predictor 2) as a score ≥6/10 for fatigue, back pain and/or physical function. Residual disease (outcome) was defined as presence of ≥1 patient-experienced (fatigue, back pain and/or physical function ≥4/10) or objective disease indicator (active peripheral manifestations, active psoriasis, elevated C-reactive protein or physician's impression) after achieving ID/LDA. Associations between either predictor and residual disease were investigated using logistic regression. RESULTS Overall, 133 patients (58 [43.6%] female, mean age 48.8 [SD 14.5] years) were included. At the HDA time-point, 16 (12.0%) patients had VHDA status and 107 (80.5%) experienced severe symptoms. At the ID/LDA time-point, prevalence of patient-experienced and objective residual disease was 70.7% (n=94/133) and 54% (n=37/68), respectively. VHDA status when in HDA state was not associated with either form of residual disease after achieving ID/LDA. Severe symptoms were associated with patient-experienced residual disease (OR=5.09 [95%CI 1.76-14.71]), but not objective residual disease. CONCLUSION Severe symptoms when in HDA state predict patient-experienced, but not objective, residual disease in axSpA, while VHDA status does not predict either form. These findings may aid in anticipating residual disease and guiding management.