AB0871 Predictive values of inflammatory low back pain, positive hla b 27 antigen, increased c reactive protein, postive magnetic resonance and other features in axial spondiloarthritis (SPA). a prospective 2 years follow up
Authors: L.Y. Komsalova, A. Valdivia, P.M. Salinas
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Diagnosis of Spondyloarthritis remains challenging in the daily practise. Inflammatory back pain might be a good tool for early diagnosis. <h3>Objectives</h3> To analyse sensitivity, specificity and predictive values of inflammatory back pain (IBP), positive HLA B27 antigen, increased C-reactive protein (CRP), positive sacroiliac joints (SI) magnetic resonance (MRI) imaging, additional features (AF) such as peripheral arthritis, dactylitis, psoriasis, uveitis, inflammatory bowel disease (IBD) and familiar history (FH) and assesse probabilities to develop SPA. <h3>Methods</h3> We prospectively collected and follow up 82 patients referred to our department with suspicion of SPA from September 2014 to December 2016. Data such as IBP, HLA B27, additional features, familiar history of SPA, increased CRP, sacroiliac x-Rays and sacroiliac MRI imaging was performed for each patient. Each MRI image was separately and independently evaluated by rheumatologist and radiologist. <h3>Results</h3> The average age in our study was 39.8 years with male/female ratio 0.4/1. 37 (45.1%) patients were diagnosed with axial SPA. Radiographic sacroiliitis had only 5 (6.1%) patients. AF had 21 (25.6%) patients. IBP was found in 36 (43.9%) patients, positive HLA B 27 antigen in 24 (29.3%) and increased CRP in 22 (26.8%). Sacroiliac joints (SI) MRI images were assessed as clearly positive if patients had more than 2 highly specific for SPA bone marrow oedema (BME) lesions, at least 3 fatty lesions and more than 1 erosion, positive MRI image if patients had at least 2 highly specific BME lesions, and clearly negative MRI images if patients had not got any of those features. We found 83.78% sensitivity and 88.89% specificity for IBP, 37.84% sensitivity and 80.95% specificity for positive HLA B27 antigen, 43.24% sensitivity and 88.1% specificity for increased CRP. AF such as such as peripheral arthritis, dactylitis, psoriasis, uveitis and IBD, evaluated together reached sensitivity 37.84% and specificity 84.44%. Positive FH only contributed to the diagnosis with 13.51% sensitivity, but showed higher specificity (84.44%). Sensitivity for positive SIJ MRI imaging were poor (51.35%) but reached excellent specificity (100%). Predictive values in our study were as follows: 86.11% predictive positive values (PPV) and 86.96% predictive negative value (PNV) for IBP, 63.64% PPV and 59.65% PNV for HLA B27, 76.19% PPV and 63.79% PNV for increased CRP, 66.67% PPV and 62.30% PNV for AF. Positive FH contributed to the diagnosis with 66.67% PPV and 62.30% PNV. Positive MRI reached 100% PPV and showed high PNV −71.43. Multivariate analysis displayed 81.8% likelihood to be diagnosed for SPA if only IBP without AF at the onset of the diagnosis and 94.8% if both IBP and AF were presented. <h3>Conclusions</h3> At the onset, IBP may be a good indicator for SPA with high sensitivity and acceptable specificity. Additional feature such as peripheral arthritis, dactylitis, psoriasis, uveitis and IBD might increase the possibility of SPA. HLA B27 antigen. increased CRP and FH brings low sensitivity for SPA nevertheless, specificity is better. Positive SI MRI imaging is highly specific but lacks sensibility. Normal SI radiography at the onset does not rule out diagnosis of SPA. <h3>Disclosure of Interest</h3> None declared