ACPA positivity plus musculoskeletal pain does not equal clinical arthritis over time for all

Not all roads lead to rheumatoid arthritis (RA), according to a decade-long study on anti-citrullinated protein antibodies (ACPA)-positive individuals with musculoskeletal pain.

Over a 10-year period, a prospective study followed Swedish patients without arthritis who tested positive for ACPA and had musculoskeletal pain, with the aim of finding out more about the disease course and prognostic factors [1]. Patients enrolled between 2010 and 2013 were followed for the development of clinical arthritis in ≥1 joint as the primary outcome, over a median period of 128 months. Additional outcomes included fulfilling ACR/EULAR classification criteria for RA.

The study cohort consisted of 82 patients with a mean age of 52 at baseline. Furthermore, 81% were women, 29% were rheumatoid factor (RF) positive, and the ACPA levels were categorised as high in 61% and low in 39% of cases.

Over the follow-up period, 63% progressed to clinical arthritis. “The median time to develop arthritis was 16 months,” Dr Simon Ahammar (Linköping University, Sweden) stated. At the 10-year clinical assessment, 40 out of the 66 (60%) patients who completed the study had developed arthritis. While all of them fulfilled the ACR/EULAR criteria for RA, 28% of them were not diagnosed with clinical RA. The diagnoses of these patients were transient arthritis without the need for a DMARD treatment (13%), osteoarthritis (8%), and psoriatic arthritis (7%).

A multivariate model identified 3 significant predictors of long-term progression to arthritis: ACPA levels (P<0.001), RF levels (P=0.020), and high RF levels (P=0.018), the latter detected after dichotomisation into high and low categories.

“Other factors, such as shared epitope or symptom duration, tender joint counts, or C-reactive protein levels, were not predictive of arthritis development,” Dr Ahammar informed. He concluded by noting that a future analysis of this cohort will include radiographic findings.

1. Ahammar S, et al. Results of a 10-year prospective follow-up of patients with musculoskeletal pain and anti-citrullinated protein antibodies -not every arthritis is rheumatoid arthritis, despite criteria fulfilment. OP0110, EULAR 2025, 11–14 June, Barcelona, Spain.

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Posted on 20 June 20258 August 2025