THU0232 Is a positive family history of spondyloarthritis relevant for diagnosing axial spondyloarthritis once hla-b27 status is known? data from the asas, desir and space cohorts
Authors: M. van Lunteren, A. Sepriano, R. Landewé, I.J. Berg, M. Dougados, L. Gossec, L. Jacobsson, R. Ramonda, M. Rudwaleit, J. Sieper, D. van der Heijde, F.A. van Gaalen
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Knowledge of a positive family history (according to the ASAS definition (ASAS PFH)) for spondyloarthritis (SpA), in particular a PFH of ankylosing spondylitis (AS) or acute anterior uveitis (AAU), is considered valuable in making a diagnosis of axSpA but clusters with HLA-B27 positivity<sup>1</sup>. So a relevant clinical question is if a PFH is still important for making a diagnosis of axSpA if HLA-B27 status is known. <h3>Objectives</h3> To investigate in three independent axSpA cohorts if an ASAS PFH, a PFH of AS or a PFH of AAU contributes to a diagnosis of axSpA in patients with known HLA-B27 status. <h3>Methods</h3> Baseline data of patients suspected of axSpA in the ASAS, DESIR and SPACE cohorts were analysed. In each cohort, univariable logistic regression models were performed with HLA-B27 status and ASAS PFH as determinants and a clinical axSpA diagnosis as outcome. The analyses were repeated in multivariable models with both determinants. Relative risks for axSpA diagnosis were calculated stratified on both HLA-B27 status and ASAS PFH (HLA-B27-/ASAS PFH- as reference). Analyses were repeated with a PFH of AS and a PFH of AAU. <h3>Results</h3> In total, 1964 patients suspected of axSpA were analysed (ASAS n=594, DESIR n=647, SPACE n=723). ASAS, DESIR and SPACE patients had a mean (SD) symptom duration of 85.7 (108.4), 18.2 (10.5) and 13.3 (7.0) months; 54%, 47% and 38% were male; 52%, 58% and 44% were HLA-B27+; 44%, 40% and 35% had sacroiliitis on imaging (MRI and/or radiographs); 62%, 45% and 53% received a clinical diagnosis of axSpA; an ASAS PFH was reported in 23%, 39% and 43%, respectively. In the univariable analysis, HLA-B27 status was significantly associated with an axSpA diagnosis in all three cohorts; ASAS: OR 6.7 (95%CI 4.7–9.8), DESIR: OR 2.1 (95%CI 1.5–2.9), SPACE: OR 6.6 (95%CI 4.7–9.2). An ASAS PFH was univariately associated with an axSpA diagnosis in SPACE (OR 1.5 (95%CI 1.01–2.0)), but not in ASAS (OR 1.4 (95%CI 0.9–2.0)) and DESIR (OR 1.0 (95%CI 0.7–1.4)). In the multivariable models, HLA-B27 status was independently associated with a diagnosis of axSpA but such an independent association was not found for ASAS PFH in any cohort (ASAS: HLA-B27 OR 6.9 (95%CI 4.7–10.2), ASAS PFH OR 0.9 (95%CI 0.6–1.4); DESIR: HLA-B27 OR 2.1 (95%CI 1.5–2.9), ASAS PFH OR 1.0 (95%CI 0.7–1.3); SPACE: HLA-B27 OR 6.6 (95%CI 4.7–9.3), ASAS PFH OR 1.0 (95%CI 0.7–1.4)). In all cohorts, the relative risk of an axSpA diagnosis was highest in HLA-B27+/ASAS PFH- patients (Abstract THU0232 – figure 1). Similar results were found for a PFH of AS and AAU (data not shown). <h3>Conclusions</h3> A PFH does not contribute to the likelihood of an axSpA diagnosis in back pain patients with a known HLA-B27 status. This suggests that asking for a PFH of SpA in patients presenting with back pain is redundant if HLA-B27 status is known. <h3>Reference</h3> [1] Ez-Zaitouni, et al. AR&amp;T2017;19(1):118. <h3>Disclosure of Interest</h3> None declared