A comparison of the performance of the Assessment of SpondyloArhritis international Society (ASAS) classification criteria, European Spondyloarthropathy Study Group (ESSG) classification criteria, and Modified New York (MNY) criteria in a cohort of Chinese spondyloarthritis patients

Abstract

BACKGROUND: The existing Modified New York (MNY) criteria and European Spondyloarthropathy Study Group (ESSG) criteria are defective in early diagnosis of patients with spondyloarthritis. The objective of this study was to reclassify a Chinese cohort of patients with previous expert-diagnosed spondyloarthritis according to the recently issued Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial spondyloarthritis and the two existing criteria, the ESSG criteria and MNY criteria and to compare the clinical characteristics including disease duration, disease activity, and spinal mobility between patients fulfilling these criteria. METHODS: Consecutive patients diagnosed by expert opinion from a tertiary centre were classified into three groups: the Ankylosing Spondyloarthritis (AS) by MNY criteria; undifferentiated spondyloarthritis (USpA) by ESSG criteria (USpA/ESSG), and those by ASAS classification criteria only (USpA/ASAS). Functional status was studied by Bath Ankylosing Spondylitis Functional Index (BASFI). Disease activity was evaluated by Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and C-reactive protein. Spinal mobility including modified Schober test and chest expansion was determined. RESULTS: A total of 128 spondyloarthritis patients (92 male and 36 female) were recruited. USpA/ASAS group identified patients with shortest disease duration (9.2±2.3 years, 11.6±3.8, 18.7±2.2 years in USpA/ASAS group, USpA group, and AS group respectively; P<0.01). USpA/ASAS and USpA/ESSG groups were better than AS group in terms of BASFI, modified Schober test and chest expansion. C-reactive protein and BASDAI were similar in the three groups. CONCLUSION: The ASAS classification criteria are shown to identify spondyloarthritis patients at an earlier stage when spinal mobility and functional status are preserved. This group of USpA patients demonstrated comparable disease activity to other groups, suggesting a need and predictably better outcome for early treatment.