Background Patients with spondyloarthritis (SpA) were classified in five subgroups: ankylosing spondylitis (AS), psoriatic arthritis, arthritis associated with inflammatory bowel disease, reactive arthritis and undifferentiated SpA (uSpA). ASAS criteria classify patients in peripheral SpA and axial SpA (axSpA), being the latest classified in two groups: classical AS and non-radiographic axSpA (nr-axSpa). Whether or not patients with nr-axSpA represent the same group of patients that used to be classified as uSpA remains unclear.
Objectives To evaluate the similarities and differences between patients with predominant axial disease classified currently as nr-axSpA versus those traditionally classified as uSpA.
Methods Baseline data from the ESPeranza program (a multicenter national initiative to early diagnose SpA between 2008 and 2011) was used. Inclusion criteria for this program were: age <45 years and inflammatory back pain plus ≥1 SpA features with symptoms duration between 3 and 24 months. Demographic, clinic, laboratory and image results were compared between two groups: 182 patients with nr-axSpA and 166 patients classified as uSpA. In order to get a deeper knowledge of the differences between nr-axSpA and uSpA, we also compared: i) 88 patients only classified as nr-axSpA, ii) 72 patients only classified as uSpA; iii) 94 patients fulfilling both criteria. Student-t test for continuous variables and Pearson Chi-square test for categorical variables were used.
Results Compared to patients classified as uSpA patients with nr-axSpA were younger, had HLA-B27 positive more frequently and higher values of CRP. On the other hand, they had history of SpA less frequently and lower values for BASDAI, BASFI and ASQoL (table). No differences were observed for gender, work incapacity, dactilitis, enthesitis, Pt's and Phy's VAS, BASMI and BASRI.
Conclusions Compared with patients traditionally classified as uSpA, patients who are currently classified as nr-axSpA are diagnosed earlier, are more frequently HLA-B27 carriers and have higher disease activity according to objective parameters. On the other hand, they report lower values for patient reported outcomes.
Disclosure of Interest None declared