Objective: The Self-Assessment of Psoriasis Symptoms - Clinical Trials (SAPS-CT) and SAPS - Real World (SAPS-RW) were simultaneously created to assess the experience of plaque psoriasis in two unique contexts.
Methods: Qualitative and quantitative research was conducted in four phases namely concept elicitation, questionnaire construction, content evaluation and psychometric evaluation.
Results: Following concept elicitation, 18 concepts were selected to inform questionnaire construction of the SAPS-CT and SAPS-RW. To accommodate each context of use, the SAPS-CT asks respondents to rate the target symptom 'at its worst' in the 24 h prior to assessment, while the SAPS-RW asks respondents to rate the target symptom "on average" in the 7 days prior to assessment. Cognitive debriefing confirmed that patients could comprehend and provide meaningful responses to both versions and, after minor modifications, resulted in 11-item questionnaires administered in an observational study (N = 200). Results from the observational study informed further item reduction (SAPS-RW to six items and SAPS-CT to nine items) and demonstrated that scores from each were reliable (Cronbach's α > 0.90, test-retest intraclass correlation coefficient >0.70), construct valid and able to differentiate among clinically distinct groups.
Conclusion: The SAPS-CT and SAPS-RW are content-valid PRO questionnaires capable of producing psychometrically sound scores when administered chronic to plaque psoriasis patients.
Keywords: PRO; chronic plaque psoriasis; context of use; instrument; psychometric; qualitative.