The 12-item Psoriatic Arthritis Impact of Disease Questionnaire: Construct Validity, Reliability, and Interpretability in a Clinical Setting

In 144 consecutive patients with PsA (81 men and 63 women, mean age of 51.4 ± 12.8 yrs, and 77 receiving biologic treatment), the PsAID-12 and other patient-reported outcomes (PRO) were collected, such as the Dermatology Life Quality Index. Each patient underwent articular and skin assessment. Construct validity: Factor analysis revealed a 2-factor result defined as the PsAID Symptom Score and the PsAID Skin Score. In determining convergent validity, significant correlations were found between the PsAID-12 and the clinical Disease Activity index for Psoriatic Arthritis (cDAPSA; ρ = 0.867, p < 0.0001). Multivariable analysis showed that the PsAID-12 is determined by the articular disease activity (cDAPSA, p < 0.0001), severity of psoriasis (PsO; physician's global assessment, p < 0.0001), and the presence of a coexisting fibromyalgia (FM; p < 0.0001). Reliability: Cronbach's alpha coefficient was 0.93 for the total PsAID-12. Interpretability: Applying the cDAPSA categorization of disease activity states, the PsAID-12 cutoff values resulted in 1.4 between remission and low disease activity (LDA), 4.1 between LDA and moderate disease activity (MDA), and 6.7 between MDA and high disease activity. The PsAID-12 is an excellent PRO to evaluate the effect of PsA. It should be carefully handled in patients with coexisting FM.