Background Early psoriatic arthritis (EPsA) is predominantly peripheral spondyloarthritis (SpA), but certain patients (pts) may have axial involvement with inflammatory back pain (IBP) and sacroiliitis (SI). Active inflammation of sacroiliac joints detected by magnetic resonance imaging (MRI) has been proposed as an important symptom of early axial SpA. Axial involvement and frequency of SI by MRI in EPsA insufficiently studied.
Objectives to investigate frequency of involvement of sacroiliac joints by MRI and x-ray, IBP and HLA B27 in peripheral EPsA.
Methods 40 (M/F – 17/23) pts with EPsA, according to the CASPAR criteria, the mean age 36.5 [28.5;49.5] yrs, mean PsA duration 13.5 [5;24] mo., mean psoriasis duration 3 [1;6] yrs. were included. All pts underwent clinical examination to determine IBP by ASAS criteria, HLA B27, x-ray of sacroiliac joints to determine definite radiographic SI (II-III grade) according to the New-York criteria. MRI of sacroiliac joints was performed in 37 pts by the apparatus “Signa Ovation” (0,35T `GE Medical Systems”). Bone marrow oedema/osteitis on STIR images by MRI are believed to be a sign of active SI (MRI-ASI). All MRI scans were checked by blinded readers. Median and quartiles [Me (Q25; Q75)], χ2, Yule's coefficient of association (Q level from-1 to 1) were performed. All p<0.05 were considered to indicate statistical significance.
Results Pts with EPsA had an high level of activity by DAS=3.99 [2.99;4.92], moderate by DAS28=4.22 [3.37;4.8]. MRI-ASI was found in 40.5% pts, definite radiographic SI – in 28.9%. IBP was found in 22 pts (55%), 12 out of them (30% out of all) had long-term (≥3 months) IBP and 10 out of them (25% out of all) had short-term IBP. HLA B27 was found in 42.5% pts. No correlations were found between MRI-ASI and DAS/DAS28 in EPsA pts. A high level of association was found between MRA-ASI and IBP in EPsA pts (Q=0.91, χ2 p<0,002) (Table 1).
A modest association was found between MRA-ASI and HLA B27 in EPsA pts, differences are not significant (Q=0.53, χ2 p<0.08) (Table 2).
Conclusions Although PsA refers to SpA, axial involvement had less than half of EPsA pts. MRI-ASI was found in EPsA only in 40.5% pts, x-ray definite SI - in less of cases (28.9%), IBP – in 55% of pts and less than one third of them had long-term IBP by ASAS criteria. MRI-ASI and x-ray definite SI was strongly associated with IBP and moderately with HLAB27. The degree of activity of peripheral arthritis doesn't have an effect on frequency of involvement of sacroiliac joints by MRI and x-ray.
Disclosure of Interest None declared
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