Performance of Different Criteria Sets for Inflammatory Back Pain in Radiographic and Nonradiographic Axial Spondyloarthritis

Introduction: It is important to recognise inflammatory back pain (IBP) for early diagnosis of ankylosing spondylitis (AS). The aims of this study were to develop a valid, reliable Bengali IBP tool and to assess the performance of different IBP criteria sets, including Calin, Berlin set 8a and 7b, and new Assessment of SpondyloArthritis International Society (ASAS) expert criteria, in radiographic axial spondyloarthritis (axSpA) and nonradiographic axSpA. Method: This case-control study was performed in three phases. The first phase involved development of an IBP tool by adding the fifth parameter of ASAS expert criteria to the National Health and Nutrition Examination Survey (NHANES) 2009–2010 arthritis questionnaires; the second phase assessed reliability by test-retest statistics among 87 participants at a 5-day interval. Finally, according to the imaging arm of ASAS axSpA classification criteria, 50 patients with axSpA were included as cases while 50 patients with chronic mechanical back pain (MBP) were included as a control. Results: The presence of IBP with SpA versus patients with MBP, detected by Calin criteria, were 76.0% versus 10.0%, by Berlin 8a were 72.0% versus 6.0%, by Berlin 7b were 58.0% versus 12.0%, and by ASAS were 64.0% versus 18.0%, respectively. Results suggested the Calin criteria set has the highest sensitivity (76.0%) and Berlin set 8a has the highest specificity (78.9%) in the differentiation of IBP from MBP. Conclusion: The performance of the new ASAS criteria was analogous to the other existing criteria sets. The highest positive likelihood ratio and odds ratio were found for Berlin set 8a criteria. The Berlin set 8a criteria can still be used in primary care practice at the first screening because of high sensitivity.