Association between inflammatory back pain features, acute and structural sacroiliitis on MRI, and the diagnosis of spondyloarthritis

Objectives: To evaluate the association between inflammatory back pain (IBP) features, acute and structural MRI findings suggestive of sacroiliitis, and diagnosis of spondyloarthritis (SpA). Methods: Data from 224 patients who underwent MRI for suspected sacroiliitis (2005–2015) was retrospectively reviewed by an expert rheumatologist for the presence of IBP features and for clinical standard of reference diagnosis. A telephone questionnaire was performed in cases of missing data. Acute and structural MRI parameters were scored by an experienced radiologist for the presence of sacroiliitis using the Assessment of Spondyloarthritis International Society (ASAS) criteria, Berlin score, and observer’s global impression (GI) scores. Association between IBP features and MRI scores, and odds ratio for SpA diagnosis, were calculated. Results: One hundred ninety-three subjects were included (119 F:74 M, mean age 39.7 ± 15.6, mean follow-up 49 ± 18 months). Fifty-two (26.9%) subjects were diagnosed with SpA. IBP scores were significantly higher in SpA patients (p < 0.001). IBP, ASAS, and GI MRI scores were significantly associated with the SpA diagnosis (p < 0.001 for all). The presence of night pain and morning stiffness was significantly associated with sacroiliac-joints’ bone marrow edema (BME, p < 0.05). Sensitivity for diagnosis of SpA was high for IBP (96%) and low for the MRI parameters (26.9–57.4%), and specificity was low for IBP (32%) and high for the MRI parameters (88.3–94.3%). Conclusions: The presence of IBP features is highly associated with diagnosis of SpA and correlates with MRI BME, all probably reflect inflammation. The combination of IBP and MRI should be the cornerstone in the clinician’s final diagnosis of SpA.