When Remission Is Not Recovery: Residual Disease After Objective Remission in Axial Spondyloarthritis. Evidence Note — URM Series

This Evidence Note develops a Universal Resonance Model (URM) interpretation of residual disease after objective remission in axial spondyloarthritis. It argues that objective improvement or treat-to-target achievement should not automatically be interpreted as full recovery or system stabilization. Using longitudinal SpA-Net registry findings reported by Smits et al. in The Journal of Rheumatology (2025), the note highlights that severe symptoms during high disease activity predicted later patient-experienced residual disease after transition to inactive or low disease activity, while very high ASDAS-defined disease activity did not predict residual disease in the same way. The note interprets this dissociation as evidence consistent with hysteresis, delayed recovery, and incomplete stabilization in coupled disease systems. Persistent fatigue, back pain, and impaired physical function may therefore function as trajectory markers rather than residual noise. This work reframes residual disease in axial spondyloarthritis from a problem of discordance after remission to a dynamic recovery problem: remission is not always recovery. The work is intended as a conceptual and evidence-based contribution to systems medicine, rheumatology, and dynamic disease interpretation within the URM framework.