Further Validation of a Questionnaire to Assess Flare in Psoriatic Arthritis: Determination of Cutoff and Longitudinal Change

Objective The previously developed FLARE questionnaire assesses the multidimensional aspects of a flare of psoriatic arthritis (PsA). We aimed to further validate this questionnaire. Methods Reanalysis of data from the ReFLAP study (ClinicalTrials.gov: NCT03119805 ), a longitudinal observational study carried out in 14 countries. Demographic, clinical, and patient-reported data were collected at baseline and 1 follow-up visit. The FLARE questionnaire (range 0-10) was completed at both timepoints (mean interval 4.5 months). Using a patient anchor question for perceived flare (yes/no), the optimal cutoff for defining a flare was obtained using receiver-operating characteristic curve analysis. Based on this cutoff, patients were compared for flare (yes/no) using clinical and patient-reported data, including composite measures of disease activity. The magnitude of score differences in patients experiencing a new flare at second visit were compared with independent samples t -scores. Results Of 147 patients, 61 (41%) reported a flare at baseline; the optimal score cutoff from the FLARE questionnaire was 4 (sensitivity 0.86, specificity 0.76) and, using this cutoff, patients in flare had significantly worse clinical and patient-reported outcomes. Of those patients reporting a flare, the most frequently affirmed items from the questionnaire referred to pain, mobility, frustration, and fatigue. Those with a new flare at the second visit had patient-reported and clinical change scores significantly worse than those not reporting a flare. Conclusion This study has provided further data on the FLARE questionnaire performance and validity. The questionnaire is ready for use in clinical trials and longitudinal observational studies.