Is the Difficult-to-Treat (D2T) concept applicable to axial spondyloarthritis?

To explore patient-defined flares in psoriatic arthritis (PsA), compared to an increase in disease activity in psoriatic arthritis (DAPSA) and to analyze the validity of a patient-reported flare question.ReFlap (NCT03119805) was a longitudinal study in 14 countries of consecutive patients with definite PsA. Patients were seen twice in the context of usual care, 4.5 ± 2.2 months apart. Flares were reported by patients and physicians at the second visit using a single question. DAPSA worsening was defined as a change to a higher DAPSA category. Agreement between the definitions of worsening was calculated by prevalence adjusted bias adjusted kappa (PABAK). Validity of patient-reported flare was assessed by comparing patients with versus without flare and transition to flares.In 222 patients, mean disease duration 10.8 ± 8.3 years, 127 (58.8%) males: disease activity was low (mean DAPSA 11.5 ± 14.0); 63.3% received a bDMARD. Patient-reported flares between the 2 visits were seen in 27% patients (for these patients, mean 2.2 ± 3.7 flares per patient, mean duration 12.6 ± 21.0 days per flare). Physician- reported flares were seen in 17.6% and worsening in DAPSA in 40.1% of patients. Agreement between definitions was moderate (PABAK = 0.32-0.59). Patients in flare had significantly more active disease than patients not in flare for all outcomes (all P < 0.001). At the patient-level, transition to flare state was associated to a worsening in disease activity and impact outcomes.Patient flares were frequent and were associated with active and symptomatic disease. These findings provide preliminary validation for patient-reported flares in PsA.