Disease activity and response assessment in psoriatic arthritis using the Disease Activity index for PSoriatic...

In this review we provide reasons to use joint specific composite measures of disease activity for psoriatic arthritis (PsA) rather than composite scores that combine several manifestations of psoriatic disease, including skin involvement. Based on a principal component analysis, which, indeed, excluded skin involvement as a major factor in PsA, the Disease Activity index for PSoriatic Arthritis (DAPSA) was validated using clinical trial and observational data. Further, disease activity states and response criteria were recently defined. The DAPSA is simply calculated by summing swollen + tender joint counts + patient pain + patient global assessments + CRP, using 66/68 joint counts. DAPSA has meanwhile been validated in other studies and has shown to have a very high level of validity, also when compared with joint sonography. Thus, DAPSA is useful in clinical practice, clinical trials and observational studies.