Difficult-to-treat Spondyloarthritis: What Are the Associated Factors

<i>Introduction:</i><i> </i>There have been significant advances in the treatment of spondylarthritis (SpA) in recent years. Despite these advances, there is still a proportion of patients who experience multiple changes in biologic, which may correspond to difficult-to-treat spondylarthritis (SPA DaT). Unlike rheumatoid arthritis, there is no consensus definition for this concept. The aim of our study is to determine the prevalence of multi-switchers with spondylarthritis, identify their characteristics, and analyse the number and reasons for switching in a Moroccan population. <i>Patients</i><i> </i><i>and</i><i> </i><i>methods:</i><i> </i>This is a comparative cross-sectional study that included patients with SpA diagnosed according to the 2009 ASAS criteria admitted to our department for targeted treatment. Sociodemographic data, comorbidities, and clinical, paraclinical, and therapeutic characteristics were collected for each patient. Multi-switchers who had received at least two biologics were considered to be SpA DaT. Their prevalence was estimated, and a comparison was made with a control group of non-multi-switchers (SpA-non-DaT). <i>Results:</i><i> </i>Two hundred and ten patients were included, 56.2% of whom were men, 63% with a long average disease duration. The prevalence of multi-switchers was 32.7%. Compared to the control group, patients in the DaT group were predominantly female (53.6% versus 39%, p=0.04), had more axial involvement (76.8% versus 91.5%, p=0.003) and peripheral joint involvement (88.4% versus 67.4%, p= 0.001) and associated fibromyalgia (33.3% versus 66.7%, p = 0.980), CsDMARD use (97.1% versus 31.9%, p= < 0.001), and corticosteroid use (34.8% versus 11.3%, p= < 0.001). Disease activity, BASDAI, ASDAS and CRP at the start of biotherapy were higher in the SPA DaT group (BASDAI: 21.8% versus 20.6%, p=0.08), (ASDAS: 46.4% versus 54.6%, p = 0.03), BASFI (27.5% versus 41.8% p=0.04) CRP (: 14.19±4.73 mg/l versus 13.7±2.1 mg/l, p = 0.01). Similarly, the time between diagnosis and use of the first biologic was longer (4 [2.25–6] years versus 3 [1–4] years, p = 0.03). All patients in the DaT group had received anti-TNFα, and 22.9% had received anti-IL17. Analysing switches between biologics in this difficult-to-treat group, the first switch was linked to primary failure in 59% of cases, secondary failure in 29% of cases, and an adverse effect in 12% of cases. In the second switch, primary and secondary failure were observed in 64% and 33% of cases, respectively, and adverse effects in 3%. Regarding the third switch, 83% had primary failure and 17% had secondary failure. <i>Conclusion:</i><i> </i>This study reveals a significant prevalence of patients with multiple treatment changes in the Moroccan population, highlighting the need for a larger patient sample to better define this condition.