Development and psychometric evaluation of the self-assessment of psoriasis symptoms (SAPS) – clinical trial and the SAPS – real world patient-reported outcomes

Abstract

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
• instrument
• context of use
• qualitative
• psychometric

Acknowledgements

Design, study conduct and financial support for the study were provided by AbbVie; AbbVie participated in the interpretation of data, review and approval of the manuscript; all authors contributed to the development of the publication and maintained control over the final content. Jeffery L. Solomon (employed by Adelphi Values) provided scientific writing assistance. Support for this assistance was funded by AbbVie Inc.

Disclosure statement

April W. Armstrong serves as investigator and/or consultant to AbbVie, Amgen, Janssen, Merck, Lilly, Novartis, Pfizer, and Modernizing Medicine. Benjamin Banderas, Catherine Foley, Jonathan Stokes, and Alan L. Shields are employed by Adelphi Values USA which received payment from AbbVie Inc. for participation in this research. Murali Sundaram is a former employee of AbbVie and may own AbbVie stock or stock options.

Additional information

Funding

Support for this assistance was funded by AbbVie Inc.