Prevalence and clinical correlates of rheumatoid factor and anticitrullinated protein antibodies in patients with idiopathic inflammatory myopathy

Abstract

ObjectiveAs rheumatoid factor (RF) and anticitrullinated protein antibodies (ACPAs) are not routinely tested in idiopathic inflammatory myositis (IIM), little is known about their prevalence and clinical implications in this patient group. In antisynthetase syndrome (ASS), presence of ACPA is reportedly associated with more severe and erosive arthritis. We aim to retrospectively determine the prevalence of RF and ACPA in a cross-sectional cohort of 121 patients diagnosed with IIM and to assess clinical associations.MethodsSerum samples from 121 patients diagnosed with polymyositis (n=30), dermatomyositis (n=41), ASS (n=37), inclusion body myositis (n=1), necrotising autoimmune myopathy (n=5) or overlap myositis (n=7) were analysed. RF was evaluated by nephelometry (Immage 800, Beckman–Coulter); anti-CCP antibodies were identified using fluoro enzyme immunoassays (Immuno-Cap 250, Thermo Fisher). Values above 40 IU/mL and 7 U/mL were considered positive for RF and ACPA, respectively.ResultsThe prevalence of RF and ACPA was 9.09% and 4.96%, respectively. No significant differences were observed between RF/ACPA positive versus negative patients. There was a numerical trend for RF-positive IIM patients to be older and have lower forced expiratory volume in 1 s levels.ConclusionsRF and ACPA are prevalent in IIM, although we detected a lower prevalence than reported in previous studies. Presence of these antibodies in patients with IIM patients is not clinically relevant in our cohort.

Sonographic findings from inflammatory arthritis due to antisynthetase syndrome

“…As described in one cohort, patients with early arthritis typically presented with a symmetric polyarthritis, and a later presentation of these symptoms was more likely to be oligoarticular or asymmetric [2]. Rheumatoid factor and ACPA can also be found in IIM, occurring in 10-15% of patients [7][8][9]. There is suggestion that the presence of RF and ACPA increases the prevalence of early joint involvement and aggressiveness of disease [5,7,9,10,22].…”

“…Rheumatoid factor and ACPA can also be found in IIM, occurring in 10-15% of patients [7][8][9]. There is suggestion that the presence of RF and ACPA increases the prevalence of early joint involvement and aggressiveness of disease [5,7,9,10,22]. Other studies, however, have suggested that RF and ACPA do not increase the prevalence of erosions [7].…”

“…There is suggestion that the presence of RF and ACPA increases the prevalence of early joint involvement and aggressiveness of disease [5,7,9,10,22]. Other studies, however, have suggested that RF and ACPA do not increase the prevalence of erosions [7]. The timing of articular involvement may be more relevant than these serologies, as the AENEAS cohort showed that early arthritis was associated with a higher prevalence of erosions, independent of serology [2].…”

“…In fact, 445 of 636 (64%) ASyS had polyarticular, symmetrical arthritis from disease onset in the American and European Network of Antisynthetase Syndrome (AENEAS network) [2]. Additional diagnostic complexity is created by the presence of rheumatoid factor (RF) and anti-citrullinated peptide antibodies (ACPA), which can be found in ASyS and may lead to more prominent and severe arthritis [7][8][9]. Recently, multicenter collaborations have characterized aspects of arthritis and its clinical presentation in the context of ASyS [2,4].…”

Difficulties in the diagnosis of antisynthetase syndrome

“…The accurate diagnosis is rendered difficult by the fact that antibodies against citrullinated peptides (anti-CCP) may be present not only in the course of RA but also in patients with antisynthetase syndrome [22][23][24]. Further studies are required to assess whether anti-CCP antibodies prognose an overlap syndrome with RA or whether they may be present in an isolated antisynthetase syndrome.…”