THU0274 Assessment of radiographic sacroiliitis on antero-posterior lumbar radiographs as compared to conventional pelvic radiographs in patients with axial spondyloarthritis
Authors: V. Rios Rodriguez, M. Llop, M. Protopopov, J. Sieper, H. Haibel, M. Rudwaleit, D. Poddubnyy
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> EULAR guidelines consider conventional radiography of sacroiliac joints (SIJs) as the first recommended imaging method in case of suspected axial spondyloarthritis (axSpA).<sup><sup>1</sup></sup> However, it is not clear whether sacroiliac joints can be reliably assessed on anteroposterior (AP) lumbar radiographs, which are often performed as a part of the diagnostic work-up in patients presented with back pain. <h3>Objectives</h3> To investigate reliability and validity of radiographic sacroiliitis assessment on AP lumbar radiographs as compared to conventional pelvic X-rays in patients with axSpA. <h3>Methods</h3> Patients from the GErman SPondyloarthritis Inception Cohort (GESPIC) were selected based on the availability of sets of pelvic and AP lumbar radiographs with visible SIJs at baseline and after 2 years of follow-up. Two trained readers (ML and VR) scored the images independently and in a random order according to the radiographic system of the modified New York (mNY) criteria (grade 0 to 4). The sacroiliitis sum score (0–8) was calculated as a sum of the mean grades of 2 readers for the right and left SIJ. We assessed intra- and inter-reader reliability using intraclass correlation coefficients (ICC) of the sacroiliitis sum scores. Patients were classified as having radiographic axSpA (r-axSpA) when both readers agreed on the presence of definite radiographic sacroiliitis according to the mNY criteria, and non-radiographic axSpA (nr-axSpA) otherwise. <h3>Results</h3> A total of 226 sets radiographs were scored from the 113 patients included in the present study. Intra-observer agreement was good to excellent for the sacroiliitis sum score of pelvic vs. AP lumbar radiographs. Inter-observer agreement for pelvic and AP lumbar radiographs was also good to excellent: ICC at baseline: 0.81 and 0.73, respectively, at year 2: 0.76 and 0.79, respectively. A total of 62 (54.9%) and 55 (48.7%) patients were classified as r-axSpA at baseline based on evaluation of pelvic and AP lumbar radiographs, respectively. The absolute agreement on the classification was 84.9% (figure 1). A total of 17 patients (12 (10.6%) with nr-axSpA and 5 (4.4%) with r-axSpA) were classified differently based on assessment of AP lumbar as compared to conventional pelvic radiographs (figure 1). After 2 years of follow-up, progression from nr- to r-axSpA occurred in 7 patients (6.2%) and 8 patients (7.1%) classified as nr-axSpA at baseline based on pelvic or AP lumbar radiographs assessment, respectively. Regression from r- to nr-axSpA occurred in 4 patients (3.5%) and 3 patients (2.7%) on pelvic or AP lumbar radiographs, respectively, giving a respective net progression rates of 2.7% and 4.4%. <h3>Conclusions</h3> Radiographic sacroiliitis can be assessed on AP lumbar radiographs with a similar reliability as on conventional pelvic radiographs. <h3>Reference</h3> [1] Mandl P, et al. Ann Rheum Dis2015;74(7):1327–39. <h3>Acknowledgements</h3> GESPIC was financially supported by the German Federal Ministry of Education and Research (BMBF) 2000–2007. 2005–2009 complementary financial support was obtained also from Abbott/Abbvie, Amgen, Centocor, Schering-Plough, and Wyeth. Since 2010 GESPIC is supported by Abbvie. The work of Maria Llop was supported by EULAR Scientific Bursary and by FER Institution (Fundación Española de Reumatología). <h3>Disclosure of Interest</h3> V. Rios Rodriguez Consultant for: Abbvie, Novartis, M. Llop: None declared, M. Protopopov: None declared, J. Sieper Grant/research support from: Abbvie, MSD, Pfizer, Consultant for: Abbvie, MSD, Pfizer, UCB, H. Haibel: None declared, M. Rudwaleit Consultant for: Abbvie, MSD, Pfizer, UCB, D. Poddubnyy Grant/research support from: Abbvie, MSD, Novartis, Consultant for: Abbvie, BMS, MSD, Novartis, Pfizer, UCB, Speakers bureau: Abbvie, BMS, Janssen, MSD, Novartis, Pfizer, Roche, UCB