SAT0529 TWO-YEAR PROGRESSION OF FACET JOINT ANKYLOSIS ON WHOLE SPINE LOW-DOSE CT IN PATIENTS WITH RADIOGRAPHIC AXIAL SPONDYLOARTHRITIS: DATA FROM THE SENSITIVE IMAGING OF AXIAL SPONDYLOARTHRITIS (SIAS) COHORT
Authors: Rosalinde Stal, Floris A. van Gaalen, Alexandre Sepriano, Juergen Braun, Monique Reijnierse, Désirée van der Heijde, Xenofon Baraliakos
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Facet joints are difficult to visualize on conventional radiography (CR). As an alternative, CT has been used to study facet joint ankylosis in radiographic axial spondyloarthritis (r-axSpA) in parts of the spine. In the SIAS study we have shown that, with the exception of the cervicothoracic junction, which is difficult to visualize, low-dose CT (ldCT) can be used to study facet joint ankylosis in the whole spine. <h3>Objectives:</h3> To study facet joint ankylosis progression in the whole spine over two years in patients with r-axSpA. <h3>Methods:</h3> In an observational cohort, r-axSpA patients who had between 1-18 syndesmophytes on CR and ≥1 inflammatory lesion on spinal MRI underwent ldCT of the whole spine (approximately 4 mSV) with a repeated ldCT after two years. Paired ldCTs were assessed by two trained readers independently blinded to chronology. Left and right C2-C3 to L5-S1 facet joints were scored as ankylosis present (1) or absent (0). Change scores, intraclass correlation coefficients (ICCs) (two-way average, absolute agreement) and smallest detectable change (SDC) were calculated for the whole spine and per segment. Joints C2-C3 to L5-S1 were included in the analysis, with the exception of the facet joints between C5-T2, which were excluded in all patients due to high levels of missing joint scores as previously reported. For change score calculations, segments of individual patients with &gt;25% missings were excluded. Remaining missings were imputed with the segment change score mean. Total scores were calculated using only patients with no excluded segments. <h3>Results:</h3> Baseline and 2-year follow up ldCT were available in 53 axSpA patients (mean age 48.3, 85% male, 79% HLA-B27+). For reader 1, 17%, 5.7% and 3.8% of segments were excluded from the cervical, thoracic and lumbar spine for change score analysis, respectively, and 20.7% of patients were excluded for the whole spine change score analysis. For reader 2 the percentages were 15.1%, 1.9%,1.9% and 17%, respectively. Therefore, the numbers of patients differed per reader and segment. Mean scores for baseline and follow-up, mean change scores, SDCs and ICCs are presented in Table 1. ICCs for mean status scores are good to excellent, with the lowest ICCs occurring in the cervical segment. ICCs for change scores vary greatly, the lowest ICCs being in the lumbar segment, the highest in the cervical segment. The proportion of patients with change larger than 0, larger than the positive SDC and larger than the negative SDC are given in Table 2 per reader and for consensus between readers. The largest percentages of change are seen in the thoracic segment. <h3>Conclusion:</h3> Reliability of facet joint ankylosis progression was good in the whole spine but poor in the lumbar segment where little progression was seen. Over two years, a fair number of patients had progression of facet joint ankylosis with most progression occurring in the thoracic spine. These results show that using whole spine ldCT, progression of facet joint ankylosis can be studied in r-axSpA patients. <h3>Disclosure of Interests:</h3> Rosalinde Stal: None declared, Floris A. van Gaalen: None declared, Alexandre Sepriano: None declared, Juergen Braun Shareholder of: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Grant/research support from: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Grant/research support from: Abbott, Bristol Myers Squibb, Celgene, Celltrion, Chugai, Johnson &amp; Johnson, MSD, Novartis, Pfizer, Roche, UCB Pharma, Grant/research support from: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Grant/research support from: Abbvie (Abbott), Amgen, Baxter, Biogen, BMS, Boehringer, Celgene, Celltrion, Centocor, Chugai, Hexal, Janssen, Lilly, Medac, MSD (Schering-Plough), Mylan, Mundipharma, Novartis, Pfizer (Wyeth, Hospira), Roche, Sanofi-Aventis and UCB, Consultant for: Abbvie (Abbott), Amgen, Baxter, Biogen, BMS, Boehringer, Celgene, Celltrion, Centocor, Chugai, Hexal, Janssen, Lilly, Medac, MSD (Schering-Plough), Mylan, Mundipharma, Novartis, Pfizer (Wyeth, Hospira), Roche, Sanofi-Aventis and UCB, Consultant for: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Consultant for: Abbott, Bristol Myers Squibb, Celgene, Celltrion, Chugai, Johnson &amp; Johnson, MSD, Novartis, Pfizer, Roche, UCB Pharma, Speakers bureau: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Speakers bureau: Abbvie (Abbott), Amgen, Baxter, Biogen, BMS, Boehringer, Celgene, Celltrion, Centocor, Chugai, Hexal, Janssen, Lilly, Medac, MSD (Schering-Plough), Mylan, Mundipharma, Novartis, Pfizer (Wyeth, Hospira), Roche, Sanofi-Aventis and UCB, Speakers bureau: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Monique Reijnierse Grant/research support from: Funding from the Dutch Arthritis Foundation. The funding source had no role in the design and conduct of the study., Désirée van der Heijde Consultant for: AbbVie, Amgen, Astellas, AstraZeneca, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Daiichi, Eli-Lilly, Galapagos, Gilead, GlaxoSmithKline, Janssen, Merck, Novartis, Pfizer, Regeneron, Roche, Sanofi, Takeda, Union Chimique Belge, Xenofon Baraliakos Grant/research support from: AbbVie, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Centocor, Chugai, Janssen, MSD, Novartis, Pfizer Inc, Roche and UCB, Grant/research support from: AbbVie, Pfizer, Merck Sharp &amp; Dohme, UCB Pharma, Novartis, Consultant for: AbbVie, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Chugai, Janssen Biologics, Novartis, Pfizer, UCB Pharma, Galapagos, Speakers bureau: AbbVie, Chugai, Janssen, Novartis, Pfizer, UCB Pharma