How is early spondyloarthritis defined in the literature? Results from a systematic review

To identify all possible definitions of "early SpA" employed in the literature, including "early axial SpA (axSpA)" and "early peripheral SpA (pSpA)".

A systematic literature review was conducted in Medline, EMBASE and the Cochrane Library for studies that included any mention of "early SpA" or its subtypes. The proportion of studies including a definition was calculated, and the different definitions were assessed.

Out of 9651 titles identified, 336 publications reporting data from 183 studies were included. Over time, an increasing number of publications were identified. In total, 114 (62%) studies reported a specific definition: 33% of them based it on symptom duration, 31% on radiographic damage, 28% on disease duration, 5% on both symptom/disease duration and radiographic damage, and 3% on other aspects. Overall, 61 (33%) studies included the term "early axSpA", whereas 60 (33%) included "early ankylosing spondylitis (AS)". Regarding the studies that referred to "early axSpA", the most used definition was symptom/disease duration <5 years, whereas for "early AS" was symptom/disease duration <10 years. After 2010, the definition of "early axSpA" based on the absence of radiographic sacroiliitis was less used compared to before 2010 (17% vs 38%).

Over time, the term "early SpA" and its subtypes is increasingly used. More than one third of the studies did not include a definition of the term and the studies reporting one showed a large heterogeneity. These results emphasize the need for a standardised definition of early SpA.