ASAS CLassification of Axial SpondyloarthritiS Inception Cohort


The Assessment of SpondyloArthritis international Society (ASAS) group has developed classification criteria for axial spondyloarthritis (axSpA) that allow the inclusion of patients with an early form of disease that is not yet clearly visible on plain radiography. The external standard for evaluation of these criteria was the rheumatologist expert opinion of the SpA diagnosis after incorporating laboratory and imaging data with clinical evaluation. Since their introduction, some have raised concerns regarding the ASAS classification criteria as substantial differences in the prevalence estimates of axSpA have been found. A joint meeting of the ASAS and the SpA Research and Treatment Network (SPARTAN) executive boards has recommended that the ASAS classification criteria undergo further validation in a prospective cohort in North America (Canada, Mexico, and United States) under supervision of SPARTAN and in a prospective cohort in Europe and other parts of the world of patients under supervision of ASAS presenting with undiagnosed active chronic back pain to rheumatologists.


Primary study objective:

To validate the performance of the current ASAS classification criteria in a prospective combined cohort of patients presenting to a rheumatologist in North America, Europe, and other parts of the world with undiagnosed current back pain of ≥3 months duration with onset ≤45 years of age. If a specificity of ≥90% and a sensitivity of ≥75% of the original ASAS criteria will be found in the study, the ASAS criteria will be considered validated and no further analyses will be done. Only if the primary objective is not met, refinements of the criteria will be made and tested.


Study design:

Observational, longitudinal (visit at baseline and 5 years), multi-centric, worldwide study.

Study population:

Patients referred to rheumatologists with current undiagnosed back and/or buttock pain with onset ≤ 45 years and duration ≥ 3 months.

Results: Not available yet

Timelines of the project:

2020 – ongoing

Project Team

PI: Martin Rudwaleit (Bielefeld, Germany)

Study coordinator: Miranda van Lunteren (Leiden, the Netherlands)

Steering committee: Joachim Sieper (Berlin, Germany), Désirée van der Heijde (Leiden, the Netherlands), Robert Landewé (Amsterdam and Heerlen, the Netherlands),  Floris van Gaalen (Leiden, the Netherlands), Alexandre Sepriano (Leiden, the Netherlands and Lisbon, Portugal) and Pedro Machado (Londen, UK).

Publications: Not available yet