Prevalence and clinical features of early axial spondyloarthritis according to ASAS definition: a cross-sectional analysis from the reuma-check cohort.

Objectives to estimate the prevalence at diagnosis of early axial spondyloarthritis in Argentinian Reuma-Check cohort, according to ASAS definition (early axSpA) and to identify clinical, laboratory, and imaging features associated with this group in a Latin American cohort. This single-center, observational, cross-sectional study included consecutive adult patients diagnosed with axSpA. Early axSpA was defined as ≤ 2 years of axial symptoms at diagnosis. Clinical, laboratory, and imaging assessments were performed following standardized protocols. A primary analysis was conducted on the entire cohort of diagnosed patients, followed by two subgroup analyses: one including only those fulfilling the ASAS 2009 criteria and another excluding patients with psoriasis. Logistic regression was conducted to identify factors independently associated with early axSpA. Among 124 patients, 38% (n = 47) had early axSpA at diagnosis. Significant differences between early and established axSpA included smoking habit (30 vs. 51%, p = 0.02), NSAID response (58 vs. 74%, p = 0.06), family history (38 vs. 23%, p = 0.04), and radiographic sacroiliitis (37 vs. 71%, p = 0.03). Logistic regression identified family history (OR: 2.4) as an independent risk factor, whereas smoking was inversely associated (OR: 0.4). Similar patterns were observed in the ASAS-fulfilling (33%) and psoriasis-excluded (36%) subgroups. At diagnosis, approximately one third of patients meet the ASAS definition of early axSpA. These patients are characterized by a higher frequency of family history, less smoking and structural damage. These results support the feasibility and relevance of future studies including patients with early axSpA to provide further scientific evidence at earlier stages of the disease.