Performance of different criteria sets for inflammatory back pain in patients with axial spondyloarthritis with and without radiographic sacroiliitis.

It is important to recognize inflammatory back pain (IBP) for an early diagnosis of ankylosing spondylitis (AS). Assessment of Spondyloarthritis International Society (ASAS) has recently published new criteria set for diagnosing IBP. In the present study, we evaluated the performance of the new ASAS IBP criteria and to compare the performance of IBP criteria sets in axial spondyloarthritis (axSpA) patients with and without radiographic sacroiliitis. The study sample included a total of 274 patients with a diagnosis of axSpA and 50 patients with a diagnosis of chronic (>3 months) mechanical back pain (MBP). A face-to-face interview by using a standardized questionnaire addressing all the components of IBP was performed. Data about HLA-B27 status and C-reactive protein levels were obtained from the patients' charts. There were significantly more male patients (P < 0.001) in the AS group (68.6 %) than in the non-radiographic axSpA group (29.6 %) and also than in the MBP group (37.5 %). Among the criteria sets, the Calin criteria showed the best sensitivity (91.2 %), and the Berlin criteria showed the best specificity (82.4 %) in differentiation of IBP from MBP. If the morning stiffness item of the Calin criteria was defined as lasting >30 min (Calin 30), the specificity improved (72.9 %), but at a price of loss in sensitivity (82.4 %). In this study, new ASAS criteria for IBP performed almost as good as but not better than the existing criteria sets. Performances of the criteria sets were quite comparable in the differentiation of IBP from MBP in patients with and without radiographic sacroiliitis.