Differences between men and women with nonradiographic axial spondyloarthritis: clinical characteristics and treatment effectiveness in a real-life prospective cohort

Background Sex differences with regard to clinical manifestations and response to tumor necrosis factor inhibitors (TNFi) have been delineated for the radiographic form of axial spondyloarthritis (axSpA). More limited evidence for a differential effectiveness of treatment in genders exists for the nonradiographic disease state (nr-axSpA). The aim of the study was to compare demographics, clinical parameters, and response to TNFi in women versus men with nr-axSpA. Methods We compared disease characteristics of 264 women and 231 men with nr-axSpA at inclusion in the prospective Swiss Clinical Quality Management Cohort. Response to a first TNFi was assessed in 85 women and 78 men without diagnosed co-morbid fibromyalgia. The primary outcome was the proportion of patients achieving the 40% improvement in the Assessment of SpondyloArthritis international Society criteria (ASAS40) at 1 year. Additional response outcomes were evaluated as secondary outcomes. Patients having discontinued TNFi were considered non-responders. Logistic regression analyses were adjusted for baseline differences, which might potentially mediate the effect of sex on treatment response. Results Compared to men, women had a longer diagnostic delay, a higher level of perceived disease activity, and more enthesitis and were in a lower percentage HLA-B27 positive. An ASAS40 response was achieved by 17% of women and 38% of men (OR 0.34; 95% CI 0.12, 0.93;p = 0.02). A significantly lower response rate in women was confirmed in the adjusted analysis (OR 0.19; 95% CI 0.05, 0.62;p = 0.009) as well as for the other outcomes assessed. Conclusion Despite only few sex differences in patient characteristics in nr-axSpA, response rates to TNFi are significantly lower in women than in men.