Evaluation and validation of a patient completed psoriatic arthritis flare questionnaire

Objective. Evaluation of a psoriatic arthritis (PsA), multidimensional, patient-completed disease flare questionnaire (FLARE). Methods. The FLARE questionnaire was administered to 139 patients in a prospective observational study. The “gold standard” of flare was based on patient opinion. Test-retest reliability was evaluated by intraclass correlation coefficient (ICC). Disease activity was measured by the Psoriatic Arthritis Disease Activity Score (PASDAS), Group for Research and Assessment of Psoriasis and PsA (GRAPPA) Composite Exercise (GRACE), Composite Psoriatic Disease Activity Index (CPDAI), and Disease Activity Index for Psoriatic Arthritis (DAPSA). Results. The most common symptoms of a PsA flare were musculoskeletal, followed by fatigue, frustration, loss of function, and an increase in cutaneous symptoms. The test-retest ICC for the FLARE questionnaire was 0.87 (95% CI 0.72-0.94). The optimum cut-off to identify a flare of disease was 4/10 (sensitivity 0.82, specificity 0.76; area under the curve 0.85). For those patients scoring ≥ 4, the mean score for the composite measures was as follows (score for those not reporting a flare in parentheses): PASDAS 5.3 ± 1.3 (3.1 ± 1.6); GRACE 4.5 ± 1.2 (2.2 ± 1.4); CPDAI 8.9 ± 2.5 (4.7 ± 3.1); and DAPSA 38.2 ± 20.3 (16.8 ± 14.9). In a new flare, the increase in composite measure score was calculated as follows: 1 for PASDAS and GRACE, 2 for CPDAI, and 7 for DAPSA. Agreement between the definition of flare using the cut-off of 4 from the questionnaire, and that indicated by the subject in a separate, standalone question was 0.57 (Cohen κ). Conclusion. A PsA flare displays escalation of symptoms and signs across multiple domains. The FLARE questionnaire has external validity in terms of both composite disease activity and overall patient opinion about the state of their condition.