Polysopoulos, ChristosGeorgiadis, StylianosØrnbjerg, Lykke MidtbøllScherer, AlmutDi Giuseppe, DanielaHetland, Merete LundNissen, Michael JohnJones, Gareth TGlintborg, BenteLoft, Anne GitteWallman, Johan KarlssonPavelka, KarelZávada, JakubYazici, AytenSantos, Maria JoséCiurea, AdrianMöller, BurkhardMichelsen, BrigitteMielnik, PawelHuhtakangas, JohannaRelas, HeikkiPirkmajer, Katja PerdanRotar, ZigaMacDonald, RossGudbjornsson, Bjornvan der Horst-Bruinsma, Irenevan de Sande, MarleenRiek, Myriam2025-05-122025-05-122025-12Polysopoulos, C, Georgiadis, S, Ørnbjerg, L M, Scherer, A, Di Giuseppe, D, Hetland, M L, Nissen, M J, Jones, G T, Glintborg, B, Loft, A G, Wallman, J K, Pavelka, K, Závada, J, Yazici, A, Santos, M J, Ciurea, A, Möller, B, Michelsen, B, Mielnik, P, Huhtakangas, J, Relas, H, Pirkmajer, K P, Rotar, Z, MacDonald, R, Gudbjornsson, B, van der Horst-Bruinsma, I, van de Sande, M & Riek, M 2025, 'Handling of missing component information for common composite score outcomes used in axial spondyloarthritis research when complete-case analysis is unbiased', BMC Medical Research Methodology, vol. 25, no. 1, 55. https://doi.org/10.1186/s12874-025-02515-31471-2288ORCID: /0000-0003-4539-7147/work/179272651ORCID: : /0000-0003-4539-7147/work/181510742ORCID: /0000-0003-0016-7591/work/183474852https://hdl.handle.net/2164/25406Acknowledgements We thank all the patients and health care professionals who collected the data for the individual registries participating in this study (see Additional file 1) as well as EuroSpA’s coordinating centre who provided the necessary infrastructure and support for collecting, consolidating, and analysing the data.161733635engcomposite scoremissing componentscomplete-case analysismultiple imputationaxial spondylarthritisR Medicine (General)Supplementary DataDASSupplementary InformationR1Journal article10.1186/s12874-025-02515-3251