<h3>Background</h3> Psoriatic arthritis (PsA) can significantly impact patients' (pts) quality of life due to pain, fatigue and reduced physical function ^[1]. The PsA Impact of Disease-12 (PsAID-12) questionnaire is a 12-item pt-reported outcome measure developed to assess the impact of PsA on 12 physical, social and psychological domains ^[2,3]. <h3>Objectives</h3> To determine responder thresholds (clinically meaningful within-pt improvement) and disease activity thresholds for the PsAID-12 total and single-item domain scores for pts with active PsA to complement preliminary thresholds published for the total score ^[2,4]. <h3>Methods</h3> Pooled data from two phase 3 trials (BE OPTIMAL [NCT03895203] and BE COMPLETE [NCT03896581]) of subcutaneous bimekizumab 160 mg every 4 weeks (wks) were used to estimate responder and disease activity thresholds for the PsAID-12 in pts with moderate-to-severe PsA. Each study included a 16-wk double-blind, placebo-controlled phase; BE OPTIMAL included an adalimumab reference arm. Data used were observed scores at baseline (BL) and Wk 16 for all randomised pts with ≥1 non-missing PsAID-12 single-item domain score at any scheduled visit. Anchor-based analyses (using the American College of Rheumatology [ACR] response criteria and PsA Disease Activity Score [PASDAS]) and distribution-based analyses (one standard error of measurement, and half of the baseline standard deviation [SD]) were used to determine responder thresholds at Wk 16. The maximum Youden index values from the receiver operating characteristic (ROC) curve analyses (using PASDAS and Disease Activity Index for PsA [DAPSA] scores as anchors; <b>Figure 1</b>) were used to determine disease activity thresholds. <h3>Results</h3> In 1,252 pts, mean (SD) PsAID-12 total score decreased from 4.19 (1.94) at BL to 2.65 (2.02) at Wk 16. Single-item domain scores ranged from 1.34 (2.13) for depression to 5.56 (2.26) for pain at BL and from 0.91 (1.80) for depression to 3.76 (2.51) for pain at Wk 16. The Wk 16 responder threshold for the PsAID-12 total score was identified as a 2-point decrease. For 8 PsAID-12 single-item domain scores, Wk 16 responder thresholds were identified as 3-point decreases. For the remaining 4 single-item domains (anxiety, fear and uncertainty; embarrassment and/or shame; social participation; depression), responder thresholds could not be determined due to floor effects at BL (absence of these symptoms in a high proportion of pts). Disease activity thresholds for the PsAID-12 total score were identified: ≤1.15, &gt;1.15–≤1.95, &gt;1.95–≤3.60 and &gt;3.60 for Remission, Low, Moderate and High Disease Activity, respectively (<b>Figure 1</b>). Disease activity thresholds for PsAID-12 single-item domain scores are reported in the <b>Table 1</b>. <h3>Conclusion</h3> This analysis defined responder and disease activity thresholds for the PsAID-12 total score and most single-item domain scores, which can be used to assess treatment efficacy and disease impact in pts with PsA. <h3>References</h3> [1]Gudu T. Expert Rev Clin Immunol 2018;14(5):405–17 [2]Gossec L. Ann Rheum Dis 2014;73:1012–9 [3]Orbai AM. J Rheumatol 2019;46(8):990–5 [4]Holland R. Ann Rheum Dis 2018;77:343–7. <h3>Acknowledgements</h3> This study was funded by UCB Pharma. Medical writing support was provided by Costello Medical, funded by UCB Pharma. <h3>Disclosure of Interests</h3> Laure Gossec Consultant of: AbbVie, Amgen, BMS, Celltrion, Eli Lilly, Galapagos, Janssen, MSD, Novartis, Pfizer, Sandoz and UCB Pharma, Grant/research support from: Sandoz and UCB Pharma, Laura Coates Speakers bureau: AbbVie, Amgen, Biogen, Celgene, Eli Lilly, Galapagos, Gilead, GSK, Janssen, medac, Novartis, Pfizer and UCB Pharma, Consultant of: AbbVie, Amgen, BMS, Boehringer Ingelheim, Celgene, Domain, Eli Lilly, Gilead, Galapagos, Janssen, MoonLake, Novartis, Pfizer and UCB Pharma, Grant/research support from: AbbVie, Amgen, Celgene, Eli Lilly, Gilead, Janssen, Novartis, Pfizer and UCB Pharma, Ana-Maria Orbai Consultant of: BMS, Janssen, Sanofi and UCB Pharma, Grant/research support from: Research grants to Johns Hopkins University from AbbVie, Amgen and Janssen, Maarten de Wit Speakers bureau: Over the last five years Stichting Tools has received fees for lectures or consultancy provided by Dr. Maarten de Wit from Celgene, Eli Lilly, Janssen-Cilag, Pfizer and UCB Pharma, Consultant of: Over the last five years Stichting Tools has received fees for lectures or consultancy provided by Dr. Maarten de Wit from Celgene, Eli Lilly, Janssen-Cilag, Pfizer and UCB Pharma, Christopher Pelligra Grant/research support from: Employee of Evidera, a part of Thermo Fisher Scientific that receives funding for research from UCB Pharma, Employee of: Evidera, Jérémy Lambert Shareholder of: UCB Pharma, Employee of: UCB Pharma, Valerie Ciaravino Shareholder of: UCB Pharma, Employee of: UCB Pharma, Barbara Ink Shareholder of: UCB Pharma, AbbVie and GSK, Employee of: UCB Pharma, Vanessa Taieb Employee of: UCB Pharma, Dafna D Gladman Consultant of: AbbVie, Amgen, BMS, Eli Lilly, Galapagos, Gilead, Janssen, Novartis, Pfizer and UCB Pharma, Grant/research support from: AbbVie, Amgen, Eli Lilly, Janssen, Novartis, Pfizer and UCB Pharma.