OP0323 USEFULNESS OF UNIVERSAL ANTINUCLEAR ANTIBODIES TESTING IN EARLY ARTHRITIS REFERRALS

Abstract

Background The CHUC Early Arthritis Clinic, founded in 2011, intends to provide a prompt response to patients with recent onset of symptoms suggestive of an inflammatory rheumatic disease (IRD). By research protocol, all patients are screened at baseline for the presence of antinuclear antibodies (ANA). An analysis was performed to evaluate the usefulness of universal ANA testing in these patients. Objectives To evaluate the prevalence and clinical correlates of ANA positivity in early arthritis referrals. Methods A retrospective study of consecutive patients referred to the Early Arthritis Clinic between 2011 and 2018 was conducted. Referral is based on the fulfillment of specific criteria: presence of arthritis or clinically suspected arthralgia beginning in the previous 12 months plus suggestive laboratorial abnormalities (rheumatoid factor, C-reactive protein or erythrocyte sedimentation rate). ANA titer (positive= ≥1:160) and cellular staining patterns were assessed by indirect immunofluorescence (Hep-2 cells). Positive (PPV) and negative predictive values (NPV) of an ANA positive test for the diagnosis of an IRD or an ANA-related rheumatic disease (ARD) were determined, along with PPV for the other referral criteria. Results 207 patients were included in the analysis (64.3% female, aged 53.9 ± 18.2 years). The diagnosis of an IRD was confirmed by the rheumatologist in 61.4% of cases, including 11.8% cases of ARD. The most prevalent diagnosis was rheumatoid arthritis (21.7%), followed by unclassified arthritis (8.7%), psoriatic arthritis, osteoarthritis and fibromyalgia (6.8% each). The prevalence of ANA positivity in our cohort was 64.2%, most frequently in low titration (1:160 in 33.8%, 1:320 in 19.3%, 1:640 in 8.7% and 1:1280 in 2.4%) and with a dense fine speckled pattern (45.1%). ANA-positive patients were older (53.7 ± 17.9 versus 47.9 ± 18.5, p=0.05), more likely to have an IRD (72.9% versus 40.5%, p Conclusion Early Arthritis Clinic referred cohort has a high prevalence of IRD but a low prevalence of ARD which explains the poor predictive value of ANA in this setting, especially when considering lower titters and when compared with specific referral criteria. Thus, universal ANA testing in Early Arthritis Clinic referrals seems unjustified, given its costs and added value. Studies designed to optimize the use of ANA in this context are warranted. Disclosure of Interests None declared