OP0323 Are gender-specific approaches needed in diagnosing early axial spondyloarthritis? data from the spondyloarthritis caught early cohort
Authors: A. Ortolan, M. van Lunteren, S. Ramiro, R. Ramonda, R. Landewé, H. Dagfinrud, L. Jacobsson, D. van der Heijde, F.A. van Gaalen
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Although gender differences have been observed in the severity of axial spondyloarthritis (axSpA), gender differences in disease presentation of early axSpA have not been thoroughly investigated. <h3>Objectives</h3> Our aim was to assess if the disease presents differently in males and females, and to evaluate if this has an impact on the diagnostic process. <h3>Methods</h3> Baseline data from the SPondyloArthritis Caught Early cohort, which includes patients with chronic back pain (CBP;≥3 months,≤2 years, onset &lt;45 years), were analysed. Patients underwent a full diagnostic workup, including MRI and radiograph of the sacroiliac joints (MRI-SIJ and X-SIJ), to establish a diagnosis of axSpA. Characteristics of male and female patients with a definite diagnosis of axSpA (based on a level of confidence about the diagnosis ≥7, as expressed by the physician on a 0–10 rating scale) were compared. Regression models were built for 1) the whole CBP cohort stratified by gender to study which SpA features were associated most with diagnosis in each gender, and 2) for axSpA patients to test if gender was associated with imaging positivity (MRI SIJ+and/or X-SIJ+). <h3>Results</h3> Of the 719 CBP patients, 275 were male. With 146/275 (53.1%) males and 155/444 (34.9%) females diagnosed as axSpA, males were more likely to be diagnosed with axSpA (OR 2.1, 95% CI: 1.5 to 2.9). Despite similar symptom duration, male axSpA patients were younger at diagnosis (27.4±7.5 vs 29.5±7.8 years; p=0.021). Presence of SpA features was similar in male and female axSpA patients (table 1) except for HLA-B27 and imaging positivity, which were more common in male axSpA patients (HLA-B27 +80% vs 60%; p&lt;0.0001 and positive imaging 78% vs 64%; p=0.007). Nevertheless, both these SpA features were still more prevalent in female axSpA patients than in non-axSpA patients, either females (HLA-B27 +23% and imaging 7%) or males (HLA-B27 +34% and positive imaging 11%) (all p&lt;0.001). Moreover, in multivariable models with diagnosis as outcome, HLA-B27 and imaging positivity were associated with a diagnosis of axSpA in both sexes (male patients: HLA-B27+: OR 3.8, 95% CI: 1.7 to 8.8; MRI-SIJ+: OR 24.3, 95% CI: 9.7 to 60.6; X-SIJ+: OR 2.7, 95% CI: 0.7 to 9.4 and female patients: HLA-B27+: OR 6.7 95% CI: 3.2 to 14.0; MRI-SIJ+: OR 32.6 95% CI: 14.2 to 75.0; X-SIJ+: OR 6.9 95% CI: 1.4 to 32.7). In models with imaging positivity as the outcome, male gender and HLA-B27 positivity were both independently associated with MRI+and/or X-SI+ (OR 1.8, 95% CI: 1.0 to 3.1 and OR 1.8 (1.0–3.3). <h3>Conclusions</h3> Although our data show clear gender differences in early axSpA, they highlight that in bother genders HLA-B27 and imaging are key elements for a diagnosis of axSpA. Therefore, our study does not suggests that separate diagnostic strategies are required for men and women. <h3>Disclosure of Interest</h3> None declared