Background Rheumatoid arthritis (RA) associated autoantibodies including anti-cyclic citrullinated peptide antibodies (ACPA) and rheumatoid factor (RF) may be present years before clinical presentation. The pre-clinical phase of RA may also be associated with subtle CRP elevations.
Objectives The study aimed to test whether CRP levels and positive ACPA autoantibodies in pre-clinical disease may be associated with small joint imaging demonstrable synovitis.
Methods 21 patients identified from primary care and rheumatology clinics who were ACPA positive with musculoskeletal symptoms but without clinical synovitis, underwent 3T MRI scans of joints that were clinically uninvolved, but where early RA typically presents, namely the wrist, hand and forefeet. Pre- and post-contrast sequences images were scored blindly by 2 musculoskeletal radiologists for synovitis, bone oedema and erosions.
Results 91% (19/21) patients were female, median age was 51 years and median duration of early morning stiffness (EMS) 12.5 min (range 0 to 240 min). All were ACPA+ and 57% (12/21) were RF+. Median ESR at study entry was 14.5 mm/h (range 1-40 mm/h) and median CRP using a high sensitivity CRP (hs-CRP) test was 2.7 mg/L (range <0.01 to 29 mg/L). CRP levels for 14/21 (66.7%) patients fell within the normal range (<10mg/L) and x-ray erosions were not evident.
All 21 cases had MRI determined synovitis. Synovitis was most frequently detected in the wrist (90.5% (19/21)). MCP synovitis was reported in 52.4% (11/21) and involvement of one or both forefeet in 66.7% (14/21). MRI determined bone oedema was evident in 52.4% (11/21) cases with 23.8% (5/21) documented in the wrists, 14.3% (3/21) in the MCPs and 33.3% (7/21) in the forefeet. MRI evident erosive change was noted in 13/21 (61.9%) of patients on MRI – 28.6% (6/21) in the wrists, 14.3% (3/21) in the MCPs and 42.9% (9/21) in the forefeet.
Similar proportions of MRI changes were documented in patients who had (1) elevated CRP levels (>10mg/L) and (2) normal CRP levels (<10mg/L), including the subgroup with (3) low CRP levels detected only using a high sensitivity test (hs-CRP 0.1-5 mg/L). Synovitis was documented in each of the 3 subgroups in 7/7 (100%), 14/14 (100%) and 11/11 (100%) patients, bone oedema in 3/7 (42.9%), 8/14 (57.1%) and 5/11 (45.5%) patients and erosions in 5/7 (71.4%), 8/14 (57.1%) and 6/11 (64.5%) patients respectively.
Conclusions This MRI imaging study of small joints in ACPA positive patients who do not have clinical evidence of joint inflammation showed that patients already have MRI determined small joint synovitis, irrespective of CRP levels. In these patients, musculoskeletal symptoms may be an early indicator of the presence of clinical synovitis. The study is ongoing to determine the specificity of these findings.
Disclosure of Interest None Declared
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