THU0532 SEMIQUANTITATIVE ANALYSIS OF BONE SCINTIGRAPHY TO PREDICT SPINAL PROGRESSION IN EARLY AXIAL SPONDYLOARTHRITIS: A PILOT STUDY

Background: Axial spondyloarthritis (axSpA) is a chronic inflammatory disease that typically affects the axial joint and enthesis. Abnormal hyperplasia of osteoblasts in the vertebral corner is the underlying pathogenesis of syndesmophyte formation. Therefore, detecting abnormal osteoblast hyperactivity in the axial joints of patients with axSpA might be an attractive imaging modality to detect potential of spinal structural progression. Bone scintigraphy is used to evaluate the sites of active bone formation by detecting osteoblast activities and visualizing the whole skeleton at once. Therefore, bone scintigraphy is a theoretically ideal imaging modality to predict abnormal bone growth of axial joints in patients with axSpA. Objectives: To investigate whether bone scintigraphy with semiquantitative analysis in patients with early axial spondyloarthritis (axSpA) has prognostic value for predicting spinal structural progression of these patients after 2 years. Methods: The records of 53 patients with early axSpA who underwent baseline bone scintigraphy were reviewed retrospectively. The sacroiliac joint to sacrum (SIS) ratio of bone scintigraphy was measured for semiquantitative analysis, and modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) and syndesmophyte growth were calculated at baseline and after 2 years. Receiver operating characteristic (ROC) curve analysis was used to determine the cutoff for the SIS ratio of bone scintigraphy. To identify factors associated with significant spinal structural progression, univariate and multivariate logistic regression analyses were performed. Significant progression of spinal structural damage over 2 years was defined as an increase of mSASSS of at least 2 units for 2 years or new syndesmophyte growth/bridging of pre-existing syndesmophytes. Results: Multivariate regression analysis revealed obesity (P = 0.023), current smoking status (P = 0.012), and high SIS ratio of bone scintigraphy (P = 0.015) as independent predictors for worsening mSASSS by at least 2 units over 2 years. For new syndesmophyte growth/bridging of pre-existing syndesmophytes over 2 years, current smoking (P = 0.013), high SIS ratio of bone scintigraphy (P = 0.025), and pre-existing syndesmophyte (P = 0.036) were independent predictors. Conclusion: Semiquantitative analysis of bone scintigraphy (high SIS ratio) in patients with early axSpA may be useful for identifying patients at high risk for spinal structural progression after 2 years. References: [1]Gheita TA, Azkalany GS, Kenawy SA, Kandeel AA. Bone scintigraphy in axial seronegative spondyloarthritis patients: role in detection of subclinical peripheral arthritis and disease activity. Int J Rheum Dis 2015;18:553-9. [2]Kim JY, Choi YY, Kim CW, Sung YK, Yoo DH. Bone Scintigraphy in the Diagnosis of Rheumatoid Arthritis: Is There Additional Value of Bone Scintigraphy with Blood Pool Phase over Conventional Bone Scintigraphy? J Korean Med Sci 2016;31:502-9. Disclosure of Interests: None declared