Background Although the diagnostic delay in spondyloarthritis (SpA) has been significantly reduced over the last decade, studying the earliest disease phases remains challenging. Systematic screening of individuals at high risk, including first degree relatives (FDRs) of patients, might help to address this challenge.
Objectives To assess clinical, laboratory, and imaging features of SpA in seemingly healthy FDRs of ankylosing spondylitis (AS) patients.
Methods FDRs of HLA-B27 positive AS patients between an age of 18-40 years were included in Pre-SpA, a prospective inception cohort study. Clinical (including medical history, disease activity, and clinical examination), biological (HLA-B27, CRP, ESR, and calprotectin) and imaging (X-rays and MRI of the spine and sacroiliac joints (SIJ)) data were obtained. FDRs were classified according to the Assessment of Spondyloarthritis international Society for axial SpA (ASAS axSpA), ASAS peripheral SpA, the modified New York (mNY), the European Spondyloarthropathy Study Group (ESSG) and the ClASsification for Psoriatic ARthritis (CASPAR) criteria.
Results We report the baseline features of the first 51 FDRs included in this ongoing prospective study. Thirty (59%) FDRs had back pain, of whom 9 (18%)had inflammatory back pain. None of the FDRs had peripheral arthritis/enthesitis or extra-articular manifestations although 39% reported a history of arthralgia and 16% had a tender joint count of 1 or more. Three (6%) FDRs had low grade sacroiliitis on X-ray, 1 (2%) FDR had cervical syndesmophytes on X-ray, and 11 (22%) FDRs showed bone marrow oedema of the SIJ on MRI and none of the FDRs had abnormalities of the spine on MRI. Thirteen out of 51 (25%) FDRs fulfilled any of the classification criteria: 9 (18%) fulfilled the ASAS axSpA criteria, 10 (20%) fulfilled the ESSG criteria, and 6 (12%) fulfilled both the ESSG and the ASAS axSpA criteria. None of the FDRs fulfilled any of the other classification criteria. FDRs fulfilling SpA criteria had more frequently back pain and inflammatory back pain, had a higher disease activity (including BASDAI), and worse function (BASFI), but there was no difference in inflammatory parameters, peripheral and extra-articular disease, and HLA-B27 status. In addition to the 13 (25%) FDRs fulfilling SpA criteria, 6 of the 38 (16%) FDRs not fulfilling any criteria had imaging abnormalities suggestive of SpA (5 on MRI and 1 on X-ray).
Conclusions A substantial proportion of seemingly healthy FDRs of HLA-B27 positive AS patients had clinical and/or imaging abnormalities suggestive of SpA. Twenty-five percent of the FDRs were classified as having SpA. Further follow-up of this cohort will show which FDRs will develop clinically overt SpA over time, which initial features can predict this development, and which sequence of events is followed during disease development.
Disclosure of Interest None declared
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