Treatment Effectiveness in People With axSpA or PsA Starting Treatment With Bimekizumab, Risankizumab, Guselkumab, Upadacitinib, or a TNF Inhibitor

This observational study will target patients with axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA) who have started treatment with bimekizumab, upadacitinib, risankizumab, guselkumab, or a tumour necrosis factor-alpha inhibitor (e.g., adalimumab or etanercept) at NHS hospitals in the United Kingdom. Information from patients' medical records will be collected, and patients will complete surveys about their experiences with their treatment. The study will look at treatment effectiveness from both healthcare professionals' and patients' points of view.

Inclusion Criteria: * Participant has a clinical diagnosis of axial spondyloarthritis (axSpA) or psoriatic arthritis (PsA). * Participant has been prescribed advanced therapy within one month prior to enrolment in the study, to treat their axSpA or PsA. * Participant is aged 18 years or older at enrolment. Exclusion Criteria: -Participation in a clinical trial at enrolment.