Objectives The Psoriatic Arthritis Impact of Disease (PsAID) Questionnaire is a recently developed patient-reported outcome measure (PROM) of disease impact in psoriatic arthritis (PsA). We set out to assess the validity in an independent cohort of patients, estimate the minimally important difference for improvement and explore the potential of individual components of the PsAID in clinical practice.
Methods Data were collected prospectively for a single-centre cohort of patients with PsA. Construct validity was assessed by Spearman correlation with other PROMs and reliability by intraclass correlation coefficient (ICC) at 1 week. Sensitivity to change at 3 months was determined by the standardised response mean (SRM) in those patients with active disease requiring a change in treatment.
Results A total of 129 patients (mean ±SD age 52.1±13.3, 57% women, disease duration 10.2±8 years) completed the baseline questionnaires and assessments. The mean baseline PsAID12 score was 3.92±2.26 with an ICC of 0.91 (95%CI 0.87 to 0.94). The SE of measurement was 0.51 and the minimal detectable change was 1.41. There was strong correlation (r≥0.70) with most of the PROMs studied and moderate correlation with clinical outcomes (r=0.40–0.57). The SRM of the PsAID12 was 0.74 (95%CI 0.45 to 0.97). There was strong correlation with individual PsAID items and their corresponding PROM questionnaires (r≥0.67).
Conclusion The PsAID is a reliable, feasible and discriminative measure in patients with PsA. The good responsiveness of the PsAID and strong correlation of individual items with other PROMS represent an opportunity to reduce questionnaire burden for patients in studies and clinical practice.
- psoriatic arthritis
- outcomes research
- disease activity
- patient perspective
- dmards (biologic)
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Handling editor Tore K Kvien
Contributors RJH, WT, NJM and MB: conception and design of the study. RH, WT, EK, CC, NW and NJM: acquisition and/or analysis of data. RH, WT, EK, CC, NW, MB and NJM: drafting the work or revising it critically for important intellectual content and final approval of the version to be published.
Funding RJH was supported by an award from the Australian Rheumatology Association and Arthritis Australia, during the conduct of the study; grants from Celgene, outside the submitted work. NM reports personal fees from Abbvie, grants and personal fees from Celgene, personal fees from Eli Lilly, outside the submitted work. WT reports grants and personal fees from Abbvie, grants and personal fees from Celgene, personal fees from UCB, outside the submitted work. CC reports grants from Abbvie, grants from Celgene, outside the submitted work.
Competing interests None declared.
Ethics approval The study was conducted according to the principles of the Declaration of Helsinki and ethical approval was obtained from the NRES Committee Yorkshire & The Humber - Bradford Leeds.
Provenance and peer review Not commissioned; externally peer reviewed.