Disease Activity in Psoriatic Arthritis Index and Psoriatic Arthritis Impact of Disease Questionnaire: correlation and sensitivity to change in a real clinical setting.

Objectives: The performance of many outcome measures for psoriatic arthritis (PsA) is almost unknown in real clinical practice. Our objective was to study the correlation and sensitivity to change of the Disease Activity in Psoriatic Arthritis (DAPSA) index and the Psoriatic Arthritis Impact of Disease (PsAID) questionnaire in a real practice setting.
Methods: This was a prospective, open, non-controlled study that included 60 consecutive patients with PsA treated with ustekinumab. Most had been previously treated with one or more biologic therapeutic agents. The correlation (Spearman's rho coefficient) and the sensitivity to change [Standardized Mean Response (SMR)] of DAPSA and PsAID were studied. Effect size values of 0.20, 0.50 and 0.80 corresponded to low, moderate and high sensitivity to change, respectively.
Results: More than 70% of patients achieved therapeutic goals (21.7% were in remission and 50% in low disease activity according to DAPSA categories). Two out of three patients reached an acceptable symptomatic state (PsAID <4). The correlation between final values of both instruments was substantial (Spearman's rho: 0.62, p<0.0001). The SMR for the PsAID was 1.08 (0.95-1.21) and for DAPSA was 1.5 (1.37-1.63), both values corresponding to instruments with a high sensitivity to change (>0.80). The best PsAID cut-off value for identifying DAPSA remission was 3.32 with an area under the ROC curve of 0.82.
Conclusions: DAPSA and PsAID seem to be useful instruments for a more comprehensive assessment of PsA in daily practice. Our results can help to disseminate the use of these instruments in the clinical practice of many rheumatologists.