Flare in spondyloarthritis: Thresholds of disease activity variations.

Unlabelled: There is no definition of flare in spondyloarthritis (SpA). The aim of this study was to evaluate thresholds of disease activity variations using validated composite indexes.

Methods: SpA patients (ASAS criteria) prospectively followed with at least two visits, were evaluated. Patients and physician answered at each visit the question: "do you consider your SpA/patient in a state of flare?". Variations of BASDAI and ASDAS between visits were assessed and associated to the change of perception of a flare (yes/no). ROC curves were built to assess thresholds of variation in BASDAI and ASDAS associated with the change flare between visits.

Results: The patients were issued from a prospective series of 250 SpA. Ninety-nine cases with at least 2 visits were analysed. They were: 67% men, mean age 45±12 years; disease duration: 16±10 years; 84% HLA-B27 positive; purely axial SpA: 81%; PASS at baseline: 56%; mean CRP: 8.6±13.5mg/l. Mean BASDAI and ASDAS-CRP at baseline were 4.3±2.2 and 2.5±1.1, respectively. The kappa coefficient of agreement between patient and physician for considering a flare was 0.68. The main results of the ROC curves are: a variation ≥2.1 units in BASDAI (sensitivity 59%, specificity 83%), 0.8 units in ASDAS-ESR (sen 56%, spe 91%) or 1.3 units in ASDAS-CRP (sen 47%, spe 100%) is associated to a flare.

Conclusion: We propose thresholds of variations of BASDAI, ASDAS-ESR, and ASDAS-CRP associated to (and that may define) a flare, as considered by the patient and the physician.