• Alistair B Reid, Michael Wiese, Leah McWilliams, Rob Metcalf, Cindy Hall, Anita Lee, Catherine Hill, Mihir Wechalekar, Les Cleland, and Susanna M Proudman.
• Department of Rheumatology, The Royal Adelaide Hospital, Adelaide, South Australia, Australia.
• Intern Med J. 2020 Jul 1; 50 (7): 818-822.

AimTo Investigate the prevalence of seroconversion to ACPA after commencement of triple disease-modifying anti-rheumatic drug (DMARD) treat-to-target therapy.BackgroundAnti-citrullinated peptide antibody (ACPA) and rheumatoid factor (RF) define 'seropositive' rheumatoid arthritis (RA). Both predict unfavourable disease course, development of extra-articular features and treatment outcomes. We investigated the prevalence of seroconversion to ACPA after commencement of triple disease-modifying anti-rheumatic drug (DMARD) treat-to-target therapy.MethodsDMARD-naïve patients with RA according to the 1987 American College of Rheumatology criteria and disease duration of <96 weeks were enrolled. RF and ACPA levels were recorded at baseline and sequentially during triple DMARD therapy.ResultsA total of 368 patients were followed for a median of 272 weeks. Of 154 patients seronegative for ACPA at recruitment, 10 (6.5%) seroconverted at some point. Nine of these were positive for RF at baseline and baseline RF titre was predictive of seroconversion. Four (2.6%) patients remained seropositive. No patients seroconverted from negative to positive for both RF and ACPA. Median time to seroconversion for ACPA was 29 months.ConclusionPersistent seroconversion of ACPA from negative to positive after diagnosis in patients with RA is uncommon. ACPA and RF double negative patients are highly unlikely to ever develop ACPA positivity with a risk <1%. It is therefore unlikely to be helpful or cost effective to perform serial ACPA measurements in patients with seronegative RA after commencement of a treat-to-target strategy.© 2019 Royal Australasian College of Physicians.

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