Background Inflammatory back pain (IBP) is a symptom related to axial spondyloarthritis. Applying the ASAS IBP definition in a large validation cohort yielded sensitivity and specificity of 79.6% and 72.4%, respectively.
Objectives Since ASAS IBP definition was never tested in psoriatic subjects, we report here the performance of those criteria in such peculiar setting.
Methods All the subjects followed up at our dermatological clinic were consecutively referred to rheumatologist whether: a) spontaneously reporting musculo-skeletal complaints; b) the dermatologists noticed limping or articular/digital swelling.
Dermatological features (PASI score, age of onset, previous/current therapies) were recorded. All referred subjects underwent a thorough rheumatological evaluation encompassing joint counts (tender, swollen, damaged), entheses counts and others as suggested in the international consensus. Patients also underwent radiographic evaluation of painful areas, laboratory test were performed if needed.
PsA diagnosis was established through expert opinion. Subjects with incomplete data were excluded from this report.
Results Subjects referred were 277, data were available for 257 (92.8%). At enrolment females were 135 (52.5%), the mean age was 56.2 years (SD 12.8), median psoriasis duration was 10.5 years (IQR 4-19). Plaque psoriasis was prevalent (78.9%), the median PASI score was 3.2 (IQR 1.2-6), 34 subjects (13.4%) scoring ≥10. TNF-inhibitors, methotrexate, cyclosporine A or systemic steroids were given to 73 subjects (28.4%).
Spinal pain was reported by 77 subjects (30%), IBP by 25 subjects (9.7%).
Psoriatic arthritis (PsA) cases were 109 (42%), of whom 64 were diagnosed as consequence of enrolment. Psoriatic spondylitis was detected in 17 cases (15.6% of PsA), 100 subjects (41.7% of the sample) had spinal diseases other than spondylitis.
The performance of ASAS IBP definition in our sample was as follows: sensitivity 70.6%, specificity 94.6%; positive predictive value 48%, negative predictive value 97.8%; positive likelihood ratio 13.03, negative likelihood ratio 0.31.
When psoriatic spondylitidies were compared to other spinal diseases, positive and negative likelihood ratios were 6.4 and 0.95, respectively (the other parameters changed slightly).
Conclusions ASAS IBP definition showed a good performance when applied to psoriatic subjects. Although tested in a small series, the performance was more specific than the original validation.
Disclosure of Interest None declared
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