This is a prospective, observational, cohort study to collect data on adult participants who have a confirmed diagnosis of psoriatic arthritis (PsA) and are starting either STELARA or a new TNFi as a new therapy in a first, second, or third line of biologic disease-modifying antirheumatic drug (bDMARD) therapy. Approximately 1,400 participants will be enrolled into this study, with 700 participants who are receiving STELARA at study entry and 700 participants who are receiving a new TNFi therapy at study entry. Recruitment into the study will continue for approximately 2 years (with the possibility to extend this period if the patient enrollment target is not reached), with a 3-year follow-up period. For each participant, the follow-up period will continue for 3 years (36 months) after inclusion into the study. Participants will primarily be assessed for parameters of treatment retention, clinical response, effectiveness and safety over an observational period of 36 months.
