PROJECT SUMMARY / ABSTRACT Treatments for plaque psoriasis vary substantially in effectiveness and side effects. It is often difficult to determine the optimal treatment during a patient-centric, shared decision-making process between the clinician and patient. The NIH and other stakeholders consider patient-reported outcomes (PROs) crucial for the support of patient-centered care because PROs reflect the patients’ perspective and offer important information to improve clinical decision-making and care delivery. Treatment satisfaction is a key PRO that represents the patient’s experience with the process and outcome of the treatment. Patient satisfaction with their treatment is critical because it affects patients’ treatment- related behaviors, such as the likelihood of continuing to use their medication, to use the medication correctly, and to adhere to prescribed treatment regimens. These treatment-related behaviors, in turn, substantially impact the success of treatment outcomes. The overarching goal of this study is to validate a patient-reported, dermatology-specific treatment satisfaction instrument (DermSat). In this study, we plan to achieve two aims. In Aim 1, we will validate DermSat for longitudinal assessment of patient satisfaction with psoriasis treatments during stable psoriasis and flares. We will also determine if DermSat will confer good reliability. We will study this aim in a prospective, observational cohort and recruit from a diverse psoriasis patient population in southern California. In Aim 2, we will determine whether DermSat predicts medication adherence and treatment changes. Specifically, we will evaluate the predictive validity of DermSat by examining the relationship between DermSat and subsequent assessment of adherence and treatment changes. A measure with excellent predictive validity will enable clinicians to identify treatment dissatisfaction and intervene earlier to minimize the long-term impact of psoriasis. The successful completion of this research will lead to the first valid and reliable dermatology-specific treatment satisfaction instrument. The study findings will have a marked impact on future clinical trial design. DermSat will address the critical need to capture patients’ treatment experience in studies for both approved and investigative dermatological therapies. Valid assessment of patients’ treatment satisfaction will also help inform shared decision-making between clinicians and patients in clinical practice, predict treatment adherence, and improve the likelihood of long-term treatment success.