Relationship between sex and clinical and imaging features of early axial spondyloarthritis: results from a 48 month follow-up (Italian arm of the SPondyloArthritis Caught Early (SPACE) study)

Objectives: To assess the association between sex and clinical and disease activity indices, and X-rays and magnetic resonance imaging (MRI) features, in early-stage axial spondyloarthritis (axSpA). Method: Baseline data analysis was conducted on the Italian SPACE cohort, including patients with chronic back pain (duration ≥ 3 months and ≤ 2 years; onset < 45 years). Patients underwent MRI and X-rays of the sacroiliac joints (SIJs) to establish the diagnosis of axSpA, according to Assessment of SpondyloArthritis international Society criteria and physician’s judgement. Clinical features, disease activity and functional indices, and images were collected at baseline and yearly during 48 months. Spinal and SIJ X-rays and MRI images were scored by two readers following Spondyloarthritis Research Consortium of Canada (SPARCC), modified Stoke Ankylosing Spondylitis Spinal Score, and modified New York criteria. Characteristics of axSpA patients according to sex (male/female) were compared over time using descriptive statistics. Results: Ninety-one patients had axSpA (83.5% non-radiographic; 16.5% radiographic); 47.3% were male. Males were younger, with shorter duration of axial symptoms, and more frequently had HLA-B27 positivity, radiographic sacroiliitis with a bilateral/symmetric pattern, and more signs of spondylitis. Females more frequently showed peripheral/entheseal involvement and the non-radiographic phenotype. Males showed increased pelvic/spinal radiographic progression and more often had active sacroiliitis on MRI. Although the frequency of inflammatory corner lesions did not differ between males and females, localization varied, with more cervical/thoracic MRI-spine lesions in females and more lumbar lesions in males. We observed a significant downward trend of SPARCC SIJ/spine scores in all patients, irrespective of sex. More fat lesions were observed on MRI-spine in females and on MRI-SIJ in males. Conclusion: Sex was associated with distinct axSpA features: females showed low-grade radiographic sacroiliitis and spinal progression, and a higher prevalence of cervical and thoracic spine MRI signs.