Background Active sacroiliitis (SI) by magnetic resonance imaging (MRI) has been proposed as an important symptom of early spondyloarthritis (SpA) and would be helpful for the distinction between perhypheral polyarthicular psoriatic arthritis (PsA) and rheumatoid arthritis (RA) at an early stage.
Objectives To compare involvement of sacroiliac joints by MRI, frequency of inflammatory back pain (IBP) and HLA-B27 in early perypheral polyarthicular PsA and RA.
Methods 54 patients (pts) with early inflammatory polyarthritis were included, 29 (M/F – 13/16) with PsA, according to the CASPAR criteria, the mean age 36.5±11.27 yrs, the mean duration of disease 13.0±9.77 mo. and 25(M/F – 7/18) with RA, according to the ACR/EULAR 2010 criteria, the mean age 52.6±14.7 yrs, the mean duration of disease 4.0±1.72 mo. All pts underwent clinical examination (CE) to determine short-term IBP and IBP by ASAS criteria, HLA-B27 antigen test (in 27 PsA pts and in 20 RA pts) MRI of the SI joints by the apparatus “Signa Ovation” (0,35T “GE Medical Systems”) according to REMARCA (Russian InvEstigation of MethotrexAte and Biologics in EaRly ACtive Inflammatory Arthritis) protocol. Bone marrow oedema (BMO)/osteitis on STIR-images by MRI are believed to be a sign of active sacroiliitis (MRI-ASI). All MRI-scans were checked by blinded readers. Mean±SD, median and quartiles [Me (Q25; Q75)], t-test, χ2-test, Fisher’s exact, Yule’s coefficient of association (Q-level from -1 to 1) and Phi were performed. All p<0.05 were considered to indicate statistical significance.
Results Those pts with PsA and RA had an equal level of activity by DAS28 - 4.09±1.26/4.62±0.86 (t-test p>0.24). In comparison a greater number of MRI-ASI was found in PsA than in RA – 12 pts (41.4%)/3pts (12%) accordingly (Fisher’s exact, p<0.016). No correlations were found between MRI-ASI and DAS28 in PsA and RA pts. In PsA pts IBP was found in 11 pts (37.9%), 6 out of 11 pts (54.5%) had IBP by ASAS criteria and 5 out of 11 pts (45.5%) had short-term IBP. In RA group 3 pts had only mechanical back pain. In PsA HLA-B27 was found in 9 out of 27 pts (33.3%) and in 3 out of 20 RA pts (15%) (t-test p<0.014). A high level of association was found between IBP and ASI in PsA pts (Q=0.91, Phi=0.56, Fisher’s exact p<0,003) (see table 1).
A modest association was found between HLA-B27 and ASI in PsA pts (Q=0.75, Phi=0.56, Fisher’s exact p<0.039) (see table 2).
Conclusions MRI-ASI is quite common in early PsA but also can be found in early RA. In PsA pts MRI-ASI is strongly associated with IBP and moderately with HLA-B27 in most cases, so all three tests can be helpful in distinguishing polyarthicular PsA and RA at an early stage.
Disclosure of Interest None Declared