Table 1

General characteristics of the studies included (10 studies)

	Publication type	Country	Database	Sex, male/total (%)	Mean age (categorised by 40 years)	MRI sequence
Bordner et al21	Original article	France	DESIR (internal) ASAS (external)	126/256 (49) (23/47 (49) for the external cohort)	<40 years for the internal and the external cohort	STIR and T1 weighted
Ye et al22	Original article	China	Hospital	422/638 (66)	<40 years	SPAIR
Tenório et al23	Original article	Brazil	Hospital	29/46 (63)	>40 years	STIR and SPAIR
Roels et al24	Conference proceeding	Belgium	Hospital	Not reported	Not reported	T1 and T2 weighted
Lin et al25	Original article	China	Hong-Kong multicentre cohort	218/388 (56)	>40 years	STIR and T1 weighted
Bressem et al26	Original article	Multinational*	GESPIC and OptiRef (internal) ASAS (external)	245/477 (51)(46/116 (40) for the external cohort)	<40 years for the internal and the external cohort	Fluid-sensitive fat-suppressed and T1 weighted
Nicolaes et al27	Conference proceeding	Belgium	C-axSpAnd and BE MOBILE RCT	Not reported	Not reported	STIR and T1 weighted
Lee et al28	Original article	South Korea	Hospital	56/79 (71)	<40 years	Gadolinium-enhanced fat-suppressed and T1 weighted
Kepp et al29	Original article	Switzerland	Hospital	40/90 (44)	>40 years	TIRM and T1 weighted
Faleiros et al30	Original article	Brazil	Hospital	Not reported	Not reported	STIR and SPAIR

*Europe, China, Taiwan, Turkey and Colombia.
ASAS, Assessment of Spondyloarthritis International Society; DESIR, DEvenir des Spondyloarthropathies Indifferenciees Recentes; GESPIC, German Spondyloarthritis Inception Cohort; MOBILE, Evaluation of the efficacy and safety of bimekizumab in subjects with active non-radiographic axial spondyloarthritis; OptiRef, Optimal Referral Strategy for Early Diagnosis of Axial Spondyloarthritis; SPAIR, SPectral Attenuated Inversion Recovery; STIR, Short τ Inversion Recovery; TIRM, Turbo Inversion Recovery Magnitude.