Background It is known that anti-citrullinated peptide antibody (ACPA)-positive Rheumatoid Arthritis (RA) has a preclinical phase with subclinical local joint inflammation on Magnetic Resonance imaging (MRI). Whether this is also present in ACPA-negative RA is unknown.
Objectives Therefore, we studied ACPA-negative arthralgia patients that were considered prone to progress to RA for local subclinical inflammation on hand and foot using MRI.
Methods Sixty-four ACPA-negative patients without clinically detectable arthritis and with arthralgia of small joints for less than one year that because of the character of the symptoms were considered suspect to progress to RA by the rheumatologists were studied. For comparisons, 19 healthy symptom free controls and 20 ACPA-negative 1987-RA patients were evaluated. All subjects underwent MRI of unilateral wrist, MCP- and MTP-joints. Synovitis and bone marrow edema (BME) were scored according to the RAMRIS method and summed yielding the “MRI inflammation score”. Median scores were compared between groups. Within the ACPA-negative arthralgia patients, MRI inflammation scores were related to C-Reactive Protein (CRP)-levels and tenderness of the scanned joints.
Results MRI inflammation scores increased when comparing controls, ACPA-negative arthralgia and RA patients (median scores 0, 1 and 10 respectively, p<0.001). The MRI inflammation scores of ACPA-negative arthralgia patients were significantly higher than that of controls (p=0.018). In particular the synovitis scores were higher in ACPA-negative arthralgia patients (p=0.046). Within the ACPA-negative arthralgia patients, inflammation was predominantly observed in the wrist (53%). The synovitis score was associated with CRP-level (p=0.007) and joint tenderness (p=0.026). Despite the limited follow-up duration already five arthralgia patients developed clinically detectable arthritis; these patients had higher scores for MRI inflammation (p=0.001), synovitis (p=0.002) and BME (p=0.003) compared to the patients that did not develop clinical arthritis.
Conclusions Subclinical synovitis was observed in the small joints of ACPA-negative arthralgia patients; especially in patients that progressed to clinically detectable arthritis. This suggests the presence of a preclinical phase in ACPA-negative RA. Further longitudinal studies on these lesions and patients are required.
Disclosure of Interest None declared