Background/Purpose: Patient reported outcomes (PROs) have been found to be reliable indicators of baseline status, change during treatment, and are predictive of long-term outcome. A EULAR taskforce developed the PsAID questionnaire as an impact measure of psoriatic arthritis (PsA) for use in clinical trials (PsAID9) and routine practice (PsAID12). We set out to validate the PsAID in an independent prospective cohort.  

Methods: Data were collected prospectively for a single-centre cohort of PsA patients between July 2015 and January 2016.  Clinical measures and PROs including the PsAID were completed at baseline and the PsAID was repeated at 1 week.  The primary objective was to assess the reliability of the PsAID in stable patients with PsA.  Construct validity was assessed through correlation of the PsAID with other PROs including HAQ-DI, EuroQol (EQ-5D), Psoriatic Arthritis Quality of Life questionnaire (PsAQoL), Dermatology Life Quality Index (DLQI), visual analogue scale (VAS) scores for patient global assessment (PtGA), and joint global assessment (JtGA), as well as clinical measures.  The influence of sex and disease activity as measured by the modified Composite Psoriatic Disease Activity Index (mCPDAI) was also assessed.

Results: Seventy-six patients (37 males) were recruited to the study.  The median age was 56 years (IQR 14.25); 57 patients were treated with biologics, and 13 with conventional DMARDs.  The median tender joint count was 2 (IQR 7), median swollen joint count was 0 (IQR 2) and median mCPDAI was 2 (IQR 2).  Mean (SD) baseline PsAID12 score was 3.11 (2.29) and at 1 week was 3.06 (2.33).  Intraclass correlation coefficient (ICC) was 0.93 (95% CI 0.88-0.96).  Mean baseline PsAID9 score was 3.30 (2.38) and at 1 week was 3.22 (2.41) and ICC was 0.93 (95% CI 0.88-0.96).  There was a weak floor effect with 37% of scores ≤2 and 8% of scores >7.  The PsAID correlated strongly with most PROs (Table 1).  There was a significant difference between sexes, with a mean PsAID12 in males of 1.97 (2.12) and in females 4.03 (2.01).  When individual components of the PsAID12 were analysed females scored significantly higher in 9 of the 12 items.  The correlation between the PsAID12, other PROs and clinical measures was stronger in males than females (Table 1).  Out of the patients that fulfilled MDA criteria, only 1 patient had a PSAID12 score >4, the threshold for the patient acceptable symptom state (PASS).  

Conclusion: In this cohort, the PsAID questionnaire had excellent test-retest reliability.  There was a weak floor effect, likely related to the low disease activity of the cohort as measured by the mCPDAI.  There was strong to moderate correlation with clinical and PRO measures providing evidence for the construct validity of the PsAID in this cohort, however females scored significantly higher than males with overall weaker correlation.  Prospective data collection is underway to assess sensitivity to change.