The Psoriasis Longitudinal Assessment and Registry (PSOLAR) is a large observational study designed in 2007 to meet postmarketing safety commitments for infliximab and ustekinumab for the treatment of psoriasis.

Key limitations in analysis methodology identified in a comprehensive review of a potential safety risk were the inclusion of patients who used biologics before registry entry, unanticipated imbalances in patient characteristics across cohorts, and limited availability of all relevant clinical data.

Fundamental modifications to predefined analyses confirm no increased risk of major adverse cardiovascular events for ustekinumab, and emphasize the need for periodic assessment of study design and analytical methods to maintain validity in long-term observational studies.