Background The face validity1 and cross-sectional external validity2 of the Assessment of SpondyloArthritis international Society (ASAS) criteria for axial spondyloarthritis (axSpA), and its arms has been already confirmed in previous studies. However, so far, only one study3 has reported data regarding the predictive validity of such criteria after 4 years of follow-up.
Objectives To evaluate the predictive validity of the ASAS criteria and its arms after 5 years of follow-up. The predictive validity of the other axSpA sets of criteria (Amor, ESSG and mNY) was also evaluated.
Methods Patients: This analysis was performed on the DESIR cohort. A total of 708 adult (>18 and <50 years) patients presented with inflammatory back pain suggestive of axSpA (according to the rheumatologist's conviction of ≥5/10) for >3 months but <3 years duration. They were followed up every 6 months for the first 2 years and then yearly up to 5 years. Starting from month 24, as per protocol, patients could be excluded from the cohort in case another diagnosis (different from SpA) was made.
Methods: The gold standard for this analysis was the diagnosis of axSpA according to the rheumatologist at 5 years of follow-up. For this analysis, patients were considered as axSpA, if the rheumatologist at 5 years with a conviction of ≥7/10 for an axSpA diagnosis. Conversely, patients excluded as per protocol due to another diagnosis or patients with a rheumatologist conviction at 5 years of ≤3/10 for axSpA were considered as Non-axSpA. The set of criteria collected at baseline (ASAS, and its arms, Amor, ESSG and mNY: fulfilled/not fulfilled) were tested against the Rheumatologist's axSpA diagnosis (fulfilled/not fulfilled) after 5 years of follow-up. Predictive validity of all sets of criteria at baseline was evaluated by the positive predictive value (PPV).
Results In total, among the 708 patients included in the DESIR cohort at baseline, data on Rheumatologists diagnosis at 5 years was available in 454 patients; amongst them, 352 (77.5%) had an axSpA diagnosis according to the rheumatologist. Among these 352 patients, 245, 300, 291 and 88 patients fulfilled the ASAS criteria for axSpA, Amor, ESSG and modified NY criteria's respectively. Figure 1 shows the PPV (95% CI) of the different sets of criteria below.
Conclusions Predictive validity of the ASAS criteria for axSpA (including both arms) at 5 years was excellent; it is worth noting that the performances of the other criteria were also very good.
Molto A et al. Performances of the Assessment of SpondyloArthritis International Society Axial Spondyloarthritis Criteria for Diagnostic and Classification Purposes in Patients Visiting a Rheumatologist Because of Chronic Back Pain: Results From a Multicenter, Cross-Sectional Study. Arthritis Care & Research 2013;65:1472–81.
Molto A et al. Evaluation of the validity of the different arms of the ASAS set of criteria for axial spondyloarthritis and description of the different imaging abnormalities suggestive of spondyloarthritis: data from the DESIR cohort. Ann Rheum Dis 2015;74:746–51.
Sepriano A et al. Predictive validity of the ASAS classification criteria for axial and peripheral spondyloarthritis after follow-up in the ASAS cohort: a final analysis. Ann Rheum Dis. 2016;75:1034–42.
Acknowledgements The DESIR cohort is financially supported by unrestricted grants from the French Society of Rheumatology and Pfizer France.
Disclosure of Interest B. Meghnathi Grant/research support from: ASAS Society (ASAS FELLOW), A. Etcheto: None declared, A. Saraux: None declared, M. Dougados: None declared, A. Moltό: None declared
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