Background/Purpose:

Spondyloarthritis (SpA) activity varies with time and treatment, but to date no clear definition of a flare of the disease is available.

The aim of this study was to evaluate thresholds of disease activity variations using validated composite indexes

Methods:

SpA patients fulfilling ASAS criteria and prospectively followed  with at least two visits were evaluated using BASDAI, ASDAS-CRP and ASDAS-ESR. Patients and physician answered at each visit the question : “do you consider your SpA 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 : no to yes between visits.

Results:

The patients were issued from a prospective series of 250 SpA. 99 situations with at least 2 visits were analyzed. The main characteristics  of this cohort were : 67 % men , mean age 45 ± 12 years; disease duration : 16 ± 10 y; 84 % HLA-B27 positive; purely axial SpA:  81 %; PASS at baseline : 56 %; mean CRP: 8.6 ± 13.5 mg/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 reported in the table :

Variation of the activity score	Flare considered by Patient and physician	Flare considered by Physician	Flare considered by Patient
BASDAI Number of 2 visits AUC Specificity % Sensitivity %	2.1 67 0.715 83 59	2.1 97 0.671 82 53	2.1 76 0.694 83 55
ASDAS-CRP Number of 2 visits AUC Specificity % Sensitivity %	1.3 30 0.740 100 47	0.7 45 0.698 72 59	1.3 34 0.682 100 40
ASDAS-ESR Number of 2 visits AUC Specificity % Sensitivity %	0.8 28 0.779 91 56	0.8 28 0.779 91 56	0.8 31 0.759 92 50

Conclusion:

According to these results, an increase from a non-flare state of at least 2.1 units in BASDAI, 0.8 units in ASDAS-ESR or 1.3 units in ASDA-CRP is associated to (and may define) a flare, as considered by the patient and the physician.

This is the first study assessing, in current practice, thresholds of variation of activity score associated with a flare in SpA. This may help physicians in the evaluation and management of the patients with SpA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/defining-flare-in-spondyloarthritis-thresholds-of-disease-activity-variations/