Background/Purpose:  Anti-citrullinated protein antibody (ACPA)-positive and ACPA-negative rheumatoid arthritis (RA) have different genetic risk factors and underlying biological mechanisms. Therefore, we hypothesized that patients’ characteristics in the symptomatic phase before clinical arthritis has emerged are also different. We investigated this by studying the arthralgia phase of ACPA-positive and ACPA-negative patients.

Methods:  Patients included in a clinically suspect arthralgia (CSA)-cohort were followed for 2 years or until arthritis development. At inclusion, information on initial symptoms and current symptoms was obtained, physical examination and MRI performed and blood samples taken.

Results were compared between ACPA-positive and ACPA-negative CSA-patients that later developed arthritis. Results: 60 patients (25-ACPA-positive, 35 ACPA-negative) included between April 2012 and March 2016 developed arthritis. 80% of ACPA-negative patients experienced morning stiffness as an initial symptom, compared to 52% of ACPA-positive patients (p=0.022). ACPA-positive patients more often had symptoms in both upper and lower extremities than ACPA-negative patients (40% versus 6%, p=0.001). ACPA-positive patients had a longer symptom duration at first presentation (median of 21.3 weeks versus 10.4 weeks, p=0.016) but converted to arthritis quicker (median 5.7 weeks versus 17.9 weeks after inclusion, p=0.015). A combination of variables clustered ACPA-positive and ACPA-negative patients in PLS-analysis.

Conclusion:  In the phase preceding clinical arthritis, ACPA-negative and ACPA-positive arthralgia patients have different characteristics. This contributes to the notion that ACPA-positive and ACPA-negative RA are different disease subsets.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/before-clinically-detectable-arthritis-develops-acpa-positive-and-acpa-negative-arthralgia-patients-have-different-symptoms/