Aspects of methodology in assessing inflammation and damage in rheumatoid arthritis and axial spondyloarthritis

This thesis is two-fold focused on rheumatoid arthritis and axial spondyloarthritis. It covers outstanding aspects of research methodology in the assessment of inflammation and damage in patients with these diseases. The studies pertaining to the first part of the thesis focus on rheumatoid arthritis and may help to better understand the relationship between disease activity, radiographic damage and disability. More specifically, they evaluate which of the available tools (individual instruments or composite indices) is associated with radiographic damage and which of the different types of structural lesions detectable on radiographs is associated with disability. Additionally, these studies address methodological issues related to the optimal assessment of radiographic progression in clinical trials. The studies described in the second part of the thesis evaluate the benefit of supplementary tests reflecting inflammation, especially to help classifying (diagnosing) patients and to monitor disease activity. Among others, the studies described in this thesis provide data that allow a better usage of these tests in clinical practice. Overall, this thesis provide guidelines on how to assess properly rheumatoid arthritis and axial spondyloarthritis in clinical trials and in clinical practice. This precise way of assessment will lead to a better understanding and a better management of these diseases.