Georgiadis, StylianosPons, MarionRasmussen, SimonHetland, Merete LundLinde, Louisedi Giuseppe, DanielaMichelsen, BrigitteWallman, Johan KOlofsson, TorZavada, JakubGlintborg, BenteLoft, Anne GCodreanu, CatalinMelim, DanielAlmeida, DiogoProvan, Sella AarrestadKvien, Tore KRantalaiho, VappuPeltomaa, RitvaGudbjornsson, BjornPalsson, OlafurRotariu, OvidiuMacDonald, RossRotar, ZigaPirkmajer, Katja PerdanLass, KarinIannone, FlorenzoCiurea, AdrianØstergaard, MikkelØrnbjerg, L M2025-03-312025-03-312025-02-20Georgiadis, S, Pons, M, Rasmussen, S, Hetland, M L, Linde, L, di Giuseppe, D, Michelsen, B, Wallman, J K, Olofsson, T, Zavada, J, Glintborg, B, Loft, A G, Codreanu, C, Melim, D, Almeida, D, Provan, S A, Kvien, T K, Rantalaiho, V, Peltomaa, R, Gudbjornsson, B, Palsson, O, Rotariu, O, MacDonald, R, Rotar, Z, Pirkmajer, K P, Lass, K, Iannone, F, Ciurea, A, Østergaard, M & Ørnbjerg, L M 2025, 'Challenge of missing data in observational studies : investigating cross-sectional imputation methods for assessing disease activity in axial spondyloarthritis', RMD Open, vol. 11, no. 1, e004844. https://doi.org/10.1136/rmdopen-2024-0048442056-5933ORCID: /0000-0003-4539-7147/work/178815407ORCID: /0000-0003-4539-7147/work/179732470https://hdl.handle.net/2164/25237The EuroSpA collaboration has been supported by Novartis Pharma AG since 2017 and UCB Biopharma SRL since 2022. This EuroSpA study was financially supported by UCB. No financial sponsors had any influence on the data collection, statistical analyses, manuscript preparation or decision to submit.141534641engHumansCross-Sectional StudiesObservational Studies as TopicAxial Spondyloarthritis/diagnosisSeverity of Illness IndexMaleFemaleRegistriesData Interpretation, StatisticalLongitudinal StudiesAdultEurope/epidemiologySpondylarthritis/diagnosisR MedicineSupplementary DataDASLinkRJournal article10.1136/rmdopen-2024-004844111