Factors associated with residual disease in axial spondyloarthritis: results from a clinical practice registry.

OBJECTIVE: To explore residual disease, defined as substantial symptoms and disease burden despite a remission/low disease activity (described as 'LDA') state, in patients with axial spondyloarthritis (axSpA) and to determine which factors are associated with residual disease.

METHODS: For this cross-sectional observational study, one timepoint per patient was used from SpANet, a web-based monitoring registry for (ax)SpA. Patients with an Ankylosing Spondylitis Disease Activity Score (ASDAS)<2.1 (LDA) were included. Indicators of residual disease (outcomes) included fatigue (primary outcome), pain, physical functioning, health-related quality of life (HRQoL) and peripheral symptoms. Sex was the primary explanatory factor for residual disease. Other explanatory factors included demographics and disease-related factors. Associations between these factors and presence/extent of residual disease were explored using logistic/linear regression.

RESULTS: In total, 267 patients in an LDA state were included. Mean age was 50.6 (SD 14.3) years and 100 (37.5%) were female. Residual disease occurred frequently (n=114 [42.7%] had fatigue scores >4/10, n=34 [17.8%] pain >4/10), also in those in remission (ASDAS<1.3). Physical HRQoL was reduced in 27% and moderate/poor in 33%. Multivariable regression analyses showed that reported fatigue was more severe and prevalent in female patients (fatigue severity [0-10]: Bfemale =0.78, 95%CI 0.18-1.38; fatigue >4/10: ORfemale =3.29, 95%CI 1.74-6.20). Other indicators of residual disease (pain/peripheral symptoms/physical HRQoL) were also more severe and/or more prevalent in females.

CONCLUSION: Residual disease is frequent in patients with axSpA who are in an LDA state, including remission. Especially female patients report this. Future studies should address how to prevent/manage residual disease in axSpA.