BASDAI CUT-OFFS FOR DISEASE ACTIVITY CORRESPONDING TO ASDAS-ESR CUT-OFFS IN AXIAL SPONDYLARTHRITIS – RESULTS FROM THE EUROSPA COLLABORATION

S. Georgiadis, L. Midtbøll Ørnbjerg, B. Michelsen, T. K. Kvien, J. K. Wallman, D. DI Giuseppe, K. Pavelka, J. Zavada, S. Aarrestad Provan, M. J. Santos, A. M. Rodrigues, A. Ciurea, M. J. Nissen, C. Codreanu, C. Mogosan, Z. Rotar, M. Tomsic, G. Macfarlane, G. Jones, D. Nordström, A. M. Hokkanen, I. Van der Horst-Bruinsma, P. Hellamand, M. Østergaard, M. L. HetlandRigshospitalet, Copenhagen Center for Arthritis Research, Glostrup, Denmark Diakonhjemmet Hospital, Center for treatment of Rheumatic and Musculoskeletal Diseases, Oslo, Norway Sørlandet Hospital, Research Unit, Kristiansand, Norway Skåne University Hospital, Department of Clinical Sciences Lund, Rheumatology, Lund, Sweden Karolinska Institutet, Clinical Epidemiology Division, Stockholm, Sweden Charles University, Department of Rheumatology, Prague, Czech Republic Inland Norway University of Applied Sciences, Public Health Section, Elverum, Norway Hospital Garcia de Orta, Department of Rheumatology, Almada, Portugal Faculdade de Medicina da Universidade de Lisboa, Instituto Medicina Molecular, Lisbon, Portugal Nova Medical School, EpiDoC unit, CEDOC, Lisbon, Portugal Hospital dos Lusíadas, Rheumatology Unit, Lisbon, Portugal University Hospital Zurich, Department of Rheumatology, Zurich, Switzerland Geneva University Hospital, Department of Rheumatology, Geneva, Switzerland University of Medicine and Pharmacy, Center for Rheumatic Diseases, Bucharest, Romania University Medical Centre Ljubljana, Department of Rheumatology, Ljubljana, Slovenia Universitiy of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia University of Aberdeen, Aberdeen Centre for Arthritis and Musculoskeletal Health, Aberdeen, United Kingdom Helsinki University Hospital, Departments of Medicine and Rheumatology, Helsinki, Finland Helsinki University Hospital, Department of Medicine, Helsinki, Finland VU University Medical Centre, Department of Rheumatology, Amsterdam, Netherlands VU University Medical Center, Department of Clinical Immunology and Rheumatology, Amsterdam, Netherlands University of Copenhagen, Department of Clinical Medicine, Copenhagen, Denmark  Background The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is often used for classifying patients according to disease activity states. BASDAI values of 2, 4 and 6 have been applied as cut-offs for inactive disease (ID), between low disease activity (LDA) and high disease activity (HDA) and for very high disease activity (VHDA), respectively, although these cut-off values have not been validated. Objectives We aimed to (i) identify BASDAI cut-offs for disease activity states corresponding to the Ankylosing Spondylitis Disease Activity Score (ASDAS) cut-offs, and (ii) investigate the impact of gender on the BASDAI cut-offs. Methods Prospectively collected real-world data from axSpA patients receiving tumour necrosis factor inhibitors (TNFi) from countries participating in the European Spondyloarthritis (EuroSpA) Research Collaboration Network were analysed [1]. We chose the ASDAS version based on erythrocyte sedimentation rate (ASDAS-ESR) for which the cut-offs were first developed [2]. Hence, data from 10 registries in EuroSpA with available BASDAI and ASDAS-ESR were included. Analyses were restricted to patients’ first TNFi series with available data. To have the best representation of the disease activity states, follow-up data (6, 12 or 24 months) were used to select the cut-offs for ID and between LDA and HDA, while baseline data were used to select the cut-off for VHDA. We performed receiver operating characteristic (ROC) analyses to determine the optimal BASDAI values corresponding to ASDAS-ESR cut-offs using the Youden index (=sensitivity+specificity-1). Furthermore, we carried out separate ROC analyses to identify gender-specific BASDAI cut-offs. Finally, the level of agreement between the new BASDAI cut-offs and the ASDAS-ESR cut-offs was assessed. Results We included 4,672 axSpA patients (2,775 (59%) men) with a registration of both BASDAI and ASDAS-ESR at baseline and at least one follow-up visit. Mean (SD) BASDAI and ASDAS-ESR were 5.7 (2.1) and 3.3 (1.0) at baseline, and 3.0 (2.3) and 1.9 (1.0) at follow-up, respectively. The optimal BASDAI values corresponding to ASDAS-ESR 1.3, 2.1 and 3.5 were 2.1, 3.3 and 6.3, respectively (Figure 1). When comparing the BASDAI and ASDAS-ESR cut-offs, the level of agreement was lower for the VHDA cut-off compared to the other disease activity states (Table 1). The gender-specific BASDAI cut-offs corresponding to ASDAS-ESR cut-offs (i.e., 1.3, 2.1 and 3.5) were 2.1, 3.1 and 6.2 for men and 2.1, 3.3 and 6.4 for women, respectively (Figure 1). We also observed that fewer women met the ID and LDA cut-offs of <1.3 and <2.1 than men (Table 1). Conclusion The BASDAI cut-offs corresponding to ASDAS-ESR 1.3, 2.1 and 3.5 were 2.1, 3.3 and 6.3, respectively. There was no evidence of a clinically relevant difference in BASDAI cut-offs between men and women. References Ørnbjerg et al. (2019). Ann Rheum Dis, 78(11), 1536-1544. Machado et al. (2011). Ann Rheum Dis, 70(1), 47-53. Image/graph:Figure 1. ROC curves and optimal cut-offs for BASDAI corresponding to ASDAS-CRP cut-offs. AUC: area under the curve. Table 1. Statistical measures of agreement between BASDAI and ASDAS-ESR cut-offs Cut-offs between ID and LDA (follow-up) BASDAI<C1 (%) ASDAS-ESR<1.3 (%) Disc (%) SE SP κ All 42.4 33.2 15.9 0.90 0.81 0.67 Men 48.1 40.6 16.2 0.89 0.80 0.67 Women 34.0 22.5 15.3 0.92 0.83 0.63 Cut-offs between LDA and HDA (follow-up) BASDAI<C2 (%) ASDAS-ESR<2.1 (%) Disc (%) SE SP κ All 60.5 63.7 14.4 0.86 0.85 0.69 Men 63.9 71.2 15.7 0.84 0.85 0.64 Women 51.6 52.8 14.2 0.85 0.86 0.71 Cut-offs between HDA and VHDA (baseline) BASDAI>C3 (%) ASDAS-ESR>3.5 (%) Disc (%) SE SP κ All 40.8 42.5 21.9 0.72 0.82 0.55 Men 38.7 42.0 21.4 0.71 0.84 0.56 Women 44.0 43.2 23.0 0.74 0.79 0.53 C1: 2.1, 2.1 and 2.1 for all patients, men and women, respectively; C2: 3.3, 3.1 and 3.3 for all patients, men and women, respectively; C3: 6.3, 6.2 and 6.4 for all patients, men and women, respectively. C: cut-off; Disc: proportion of discordance; SE: sensitivity; SP: specificity; κ: kappa coefficient. Acknowledgements: NIL. Disclosure of Interests Stylianos Georgiadis Grant/research support from: Research grant from Novartis, Lykke Midtbøll Ørnbjerg Grant/research support from: Research grant from Novartis, Brigitte Michelsen Grant/research support from: Research grant from Novartis, Tore K. Kvien: None declared, Johan K Wallman Speakers bureau: Speaker fees from AbbVie, Amgen, Grant/research support from: Research support from AbbVie, Amgen, Eli Lilly, Novartis, Pfizer, Daniela Di Giuseppe: None declared, Karel Pavelka Speakers bureau: Speaker fees from Pfizer, MSD, BMS, UCB, Amgen, Egis, Roche, AbbVie, Consultant of: Consulting fees from Pfizer, MSD, BMS, UCB, Amgen, Egis, Roche, AbbVie, Jakub Zavada Speakers bureau: Speaker fees from Abbvie, Elli-Lilly, Sandoz, Novartis, Egis, UCB, Consultant of: Consulting fees from Abbvie, Elli-Lilly, Sandoz, Novartis, Egis, UCB, Sella Aarrestad Provan Consultant of: Boehringer Ingelheim, Grant/research support from: Boehringer Ingelheim, Maria Jose Santos Speakers bureau: Speaker fees from Abbvie, AstraZeneca, Lilly, Novartis, Pfizer, Ana Maria Rodrigues Speakers bureau: Speaking fees from Abbvie, Amgen, Consultant of: Consulting fees from Abbvie, Amgen, Grant/research support from: Research grant from Novartis, Pfizer, Amgen, Adrian Ciurea Speakers bureau: Speaking fees from AbbVie, Eli Lilly, Merck Sharp & Dohme, Novartis, Pfizer, Consultant of: Consulting fees from AbbVie, Eli Lilly, Merck Sharp & Dohme, Novartis, Pfizer, Michael J. Nissen Speakers bureau: Speaking fees from AbbVie, Eli Lilly, Merck Sharp & Dohme, Novartis, Pfizer, Consultant of: Consulting fees from AbbVie, Eli Lilly, Merck Sharp & Dohme, Novartis, Pfizer, Catalin Codreanu Speakers bureau: Speaker fees from AbbVie, Amgen, Boehringer Ingelheim, Ewopharma, Lilly, Novartis, Pfizer, Consultant of: Consultancy fees from AbbVie, Amgen, Boehringer Ingelheim, Ewopharma, Lilly, Novartis, Pfizer, Corina Mogosan: None declared, Ziga Rotar Speakers bureau: Abbvie, Novartis, MSD, Medis, Biogen, Eli Lilly, Pfizer, Sanofi, Lek, Janssen, Consultant of: Abbvie, Novartis, MSD, Medis, Biogen, Eli Lilly, Pfizer, Sanofi, Lek, Janssen, Matija Tomsic Speakers bureau: Speaking fees from Abbvie, Amgen, Biogen, Eli Lilly, Janssen, Medis, MSD, Novartis, Pfizer, Sanofi, Sandoz-Lek, Consultant of: Consulting fees from Abbvie, Amgen, Biogen, Eli Lilly, Janssen, Medis, MSD, Novartis, Pfizer, Sanofi, Sandoz-Lek, Gary Macfarlane Grant/research support from: Research grant from GSK, Gareth Jones Speakers bureau: Speaker fee from Janssen, Grant/research support from: Research grants from AbbVie, Pfizer, UCB, Amgen, GSK, Dan Nordström Speakers bureau: Speaking fees from Abbvie, BMS, Lilly, MSD, Novartis, Pfizer, Roche and UCB, Consultant of: Consulting fees from Abbvie, BMS, Lilly, MSD, Novartis, Pfizer, Roche and UCB, Grant/research support from: MSD, Anna-Mari Hokkanen Grant/research support from: Grant/research support from MSD, Irene van der Horst-Bruinsma Consultant of: Consultant for Abbvie, UCB, MSD, Novartis, Lilly, Grant/research support from: Unrestricted Grants received for investigator initiated studies from MSD, Pfizer, AbbVie, UCB. Fees received for Lectures from BMS, AbbVie, Pfizer, MSD, Pasoon Hellamand Grant/research support from: Research grant from Novartis, Mikkel Østergaard Speakers bureau: Speaker fees from Abbvie, BMS, Boehringer-Ingelheim, Celgene, Eli-Lilly, Hospira, Janssen, Merck, Novartis, Novo, Orion, Pfizer, Regeneron, Roche, Sandoz, Sanofi, UCB, Consultant of: Consultancy fees from Abbvie, BMS, Boehringer-Ingelheim, Celgene, Eli-Lilly, Hospira, Janssen, Merck, Novartis, Novo, Orion, Pfizer, Regeneron, Roche, Sandoz, Sanofi, UCB, Merete Lund Hetland Speakers bureau: Speaker for Pfizer, Medac, Sandoz, Grant/research support from: Research grants from Abbvie, Biogen, BMS, Celltrion, Eli Lilly, Janssen Biologics B.V, Lundbeck Fonden, MSD, Medac, Pfizer, Roche, Samsung Biopies, Sandoz, Novartis. Keywords: Outcome measures, Patient reported outcomes, Validation DOI: 10.1136/annrheumdis-2023-eular.617Citation: , volume 82, supplement 1, year 2023, page 420Session: Beyond the crystal ball (Poster Tours)