AB0752 PSORIATIC ARTHRITIS: OLIGOARTHRITIS AND POLYARTHRITIS PATTERN CHANGES OVER THE INITIAL YEAR OF THE PRESENTATION. A REAL-WORLD EVIDENCE REPORT FROM THE QUEBEC REGISTRY RHUMADATA®

Background: Psoriatic Arthritis (PsA) most frequently presents as a polyarthritis or (less often) as an oligoarthritis [1]. Upon reassessment, patients may change category during follow-up [2-3]. Historically, the patients in the original description of Moll and Wight had an oligoarticular presentation [4]. However, other studies have not found the same distribution in all patient populations [5]. Currently, none of the accepted diagnostic or classification criteria set for PsA consider the variation in the number of involved joints in the early phase of PsA. Objectives: To evaluate the change in pattern between oligoarticular and polyarticular psoriatic arthritis, within the first year of follow-up. Methods: Data from RHUMADATA® patients diagnosed with PsA were extracted on December 8th, 2019. In the current analysis, we consider the first year of care patients following their first encounter with clinic staff. Patients with at least two 66/68 joint counts completed during this initial year are the subjects of this analysis. Joint count classification (Oligo vs Poly) was assessed from the first and last available joint counts. Patients were classified as having a polyarticular form of PsA if 5 or more of their joints were assessed as being swollen and/or tender. Subjects with 4 or less swollen and/or tender joints were classified as oligoarticular PsA patients. Results: A total of 287 patients with at least two 66/68 joint counts are used in the present analysis. At baseline, the mean age of patients was 47.8 ± 13.5 with average disease duration of 1.6 ± 5.2 years. 49 % of patients were women. Average joint count at baseline was 7.1 ± 7.2 (swollen) and 7.1 ± 7.5 (tender) joints. Considering only 28 joints, the average was 4.2 ± 5 and 3.9 ± 4.8 for swollen and tender joints respectively. At the first joint count, 115 (40%) patients were assessed as “Oligo” and 172 (60%) as “Poly”, while 159 (55%) and 128 (45%) were similarly assessed at the last assessment. The two assessments agreed for 179 (62%) and disagreed for 108 (38%). Of the 115 patients initially classified as “Oligo”, 32 (28%) were reassessed as “Poly” within the initial year, while 76 (44%) of the 172 patients initially classified as “Poly” were reassessed as “Oligo”. All 172 patients initially classified as “Poly” initiated a DMARD during this period (167 (97%) initiated a csDMARD and 5 (3%) initiated a bDMARS). All patients initially classified as “Oligo” also initiated treatment during this period (98 (85%) and 17 (15%) of the 115 patients initially classified as “Oligo” initiated csDMARDs and bDMARD respectively). Conclusion: These observations suggest that a single assessment of joint count may be misleading in establishing the oligo or polyarticular pattern of PsA. This classification should take treatment into account. References: [1]Gladman DD, Ritchlin C, et al. Clinical manifestations and diagnosis of psoriatic arthritis. Uptodate 2019. [2]Jones SM, Armas JB, Cohen MG, et al. Psoriatic arthritis: outcome of disease subsets and relationship of joint disease to nail and skin disease. Br J Rheumatol 1994; 33:834. [3]McHugh NJ, Balachrishnan C, Jones SM. Progression of peripheral joint disease in psoriatic arthritis: a 5-yr prospective study. Rheumatology (Oxford) 2003; 42:778. [4]Wright V, Moll JM. Psoriatic arthritis. Bull Rheum Dis 1971; 21:627. [5]Gladman DD. Psoriatic arthritis. Baillieres Clin Rheumatol 1995; 9:319. Disclosure of Interests: Sana Chambah: None declared, Louis Coupal: None declared, Denis Choquette Grant/research support from: Rhumadata is supported by grants from Pfizer, Amgen, Abbvie, Gylead, BMS, Novartis, Sandoz, eli Lilly,, Consultant of: Pfizer, Amgen, Abbvie, Gylead, BMS, Novartis, Sandoz, eli Lilly,, Speakers bureau: Pfizer, Amgen, Abbvie, Gylead, BMS, Novartis, Sandoz, eli Lilly,