Understanding the paradigm of non-radiographic axial spondyloarthritis

The concept of axial spondyloarthritis (axSpA) encompasses both non-radiographic (nr-axSpA) and traditional radiographic axSpA (r-axSpA) forms. The former was conceived following the establishment of the ASAS classification criteria for axSpA, which for the first time included the use of magnetic resonance imaging of the sacroiliac joints. This facilitated the classification of patients with axSpA who did not present substantial structural damage. This conception of nr-axSpA revolutionized the classical understanding of axSpA opening new doors for research and broadening the scope of treatment to the entire spectrum of axSpA. In this sense, epidemiologic patterns of the disease were viewed anew, and early diagnosis became a primary objective in the management of the disease. However, despite these advances, this new axSpA subtype led to some concerns within the scientific community. These issues have been addressed by several studies that set out to clarify the concept of nr-axSpA. In this review, we summarize the findings of the most relevant studies including nr-axSpA and then discuss recent advances in understanding disease clinical patterns, burden of disease, and treatment effects. Current scientific research has shown subtle differences between nr-axSpA and r-axSpA. In the near future, these advances will allow for better management of individual patients across the axSpA spectrum.