The International Dermatology Outcome Measures (IDEOM) has defined a core set of domains to be measured in all psoriasis clinical trials. This set comprises the following domains: skin manifestations, psoriasis and psoriatic arthritis symptoms, health-related quality of life, investigator global, patient global, and treatment satisfaction. The next step is to define how to measure these domains. The objective of this article was to evaluate the quality of available instruments to assess ‘investigator global’ and ‘patient global’ domains to identify the most appropriate instruments.
Reviewers conducted a systematic literature review to retrieve studies on the measurement properties of instruments including either an investigator global assessment or a patient global assessment. Following the COnsensus based standards for the Selection of health Measurement INstruments (COSMIN) checklist, three independent reviewers rated the quality of each study. We then performed a qualitative synthesis of the evidence.
We identified nine investigator global assessments and three patient global assessments, reflecting substantial variability in global assessment instruments. Overall, most measures lacked evidence for content validity and feasibility. The Lattice System-Physician Global Assessment, Product of the Investigator Global Assessment and Body Surface Area, and the professional-Simplified Psoriasis Index had higher levels of evidence for validity, reliability, and/or responsiveness than the 5- and 6-point investigator global assessments. The self-assessment-Simplified Psoriasis Index was the only patient global assessment with evidence for validity, reliability, and responsiveness.
The 5- and 6-point investigator global assessments, which are the most widely used investigator global assessments in registered clinical trials, have less evidence for measurement properties as compared with the Lattice System-Physician Global Assessment, professional-Simplified Psoriasis Index, and the Product of the Investigator Global Assessment and Body Surface Area. However, all instruments lack evidence for content validity and feasibility. Further validation studies of investigator global assessments and patient global assessments are required to recommend the best global measure for psoriasis clinical trials.