Objective To test the psychometric performance of a modified Disease Activity index for PSoriatic Arthritis (DAPSA) using 28 instead of 66 swollen/68 tender joint counts (SJC/TJC).

Methods We included patients with psoriatic arthritis (PsA) from the Danish national quality registry DANBIO, divided into examination (n=3157 patients, 23987 visits) and validation cohorts (n=3154 patients, 24160 visits). We defined DAPSA28 = (28TJC × conversion factor1) + (28SJC × conversion factor2) + patient global (0–10VAS) + pain (0–10VAS) + C reactive protein (CRP) (mg/dL). Identification of the conversion factors was performed by generalised estimating equations in the examination cohort and evaluation of criterion, correlational and construct validity in the validation cohort.To read the full article, log in using your NHS OpenAthens details.