Ab1054 spondyloarthritis in first degree relatives of ankylosing spondylitis patients

Background Ankylosing spondylitis (AS) is a relatively common inflammatory rheumatic disease with a strong familial risk and heritability. Objectives The aim of this study was to examine first-degree relatives of patients diagnosed with AS to determine the presence of active sacroiliitis, fulfilment of Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial and/or peripheral spondyloarthritis (SpA), and the clinical diagnosis of SpA. Methods One hundred subjects without a previous rheumatological diagnosis with a first-degree relative treated for AS were included in the study. Clinical data were collected and rheumatological examinations were performed by trained rheumatologists. Magnetic resonance imaging (MRI) of the sacroiliac joints (SIJ) was read by a trained rheumatologist who was blinded to all patient data. Subjects were further divided into both SpA (according to ASAS classification criteria and clinician opinion) and non-SpA subgroups. Results A total of 26 subjects met ASAS classification criteria for SpA, of which the diagnosis of SpA was confirmed in 14 subjects (13 subjects met ASAS classification criteria for axial and 1 subject for peripheral SpA). In addition, 12 individuals met the clinical arm of the ASAS classification criteria for axSpA, but were not diagnosed with axSpA in the clinicians’ opinion. Active sacroiliitis as defined by MRI was present in all 13 individuals diagnosed with axSpA, 7 (54%) of whom already had advanced radiographic changes on conventional radiographs of the SIJ. In addition, active sacroiliitis defined by MRI was also present in 4 individuals who did not have back pain. The data are shown in Figure 1. Analysis of clinical characteristics showed a significant difference in CRP and BASDAI between the SpA vs. non-SpA subgroups (8.8 (±10.5) vs. 2.3 (±4.1) mg/l, p=0.0048, and 3.1 (±1.8) vs. 1.76 (±1.78), respectively). Individuals diagnosed with SpA were more likely to be HLA-B27 positive and had inflammatory back pain compared to the non-SpA subgroup (87% vs. 43%, p=0.0069 and 57% vs. 9%, p=0.0002, respectively). Individuals who were not diagnosed with SpA but met the clinical arm of the ASAS classification criteria for axSpA were excluded from the analysis. Other clinical characteristics and differences between subgroups are shown in Table 1. Conclusion In this cross-sectional study, a quarter of the relatives of patients with first-degree AS met the classification criteria for SpA, and 14% were diagnosed with SpA based on physician opinion. These individuals had a significantly higher prevalence of HLA-B27, inflammatory back pain, and disease activity indices. It should be kept in mind that in a small proportion of individuals, active sacroiliitis may be present in relatives with first-degree AS even in the absence of back pain. Table 1. Patient characteristics and subgroups differences Characteristic All SpA Non-SpA P N=100 N=14 N=74 SpA vs non-SpA Age (years), mean (SD ) 34.4 (11.3) 36.5 (10.5) 33.7 (11.4) 0.2956 Gender: Males, number (% ) 54 7 (50) 40 (54) >0.9999 BMI (kg/m2), mean (SD ) 28.8 (38.9) 24.8 (4.9) 30.2 (45.1) 0.7069 BASDAI, mean (SD) 2.0 (1.8) 3.1 (1.8) 1.76 (1.78) 0.0054* CRP (mg/L), mean (SD ) 3.4 (6.0) 8.8 (10.5) 2.3 (4.1) 0.0048* BP, number (% ) 74 14 (100) 48 (65) 0.0082* IBP, number (% ) 25 8 (57) 7 (9) 0.0002* Smokers, number (% ) 44 7 (50) 20 (27) 0.1185 Spinal distances: Schober (cm), mean (SD ) 4.8 (1.2) 4.5 (0.9) 4.9 (1.2) 0.276 chin-chest (cm), mean (SD ) 0.5 (1.4) 0.6 (2.9) 0.4 (1.0) 0.0714 fléche (cm), mean (SD ) 0.2 (1.0) 0.6 (1.6) 0.1 (1.0) 0.0873 chest expansion (cm), mean (SD ) 5.4 (1.7) 6.0 (2.0) 5.3 (1.7) 0.2773 HLA-B27 positivity, number (% ) 56 12 (86) 32 (43) 0.0069* BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BMI, Body mass index; BP, back pain; CRP, C-reactive protein; HLA, human leukocyte antigen; IBP, inflammatory back pain, * P value ˂ 0.05 REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests None Declared.