Flare in spondyloarthritis: Thresholds of disease activity variations

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.