Development and reliability testing of a standardized questionnaire to assess psoriasis phenotype

Background: Psoriasis genetics researchers have utilized separate and widely differing survey instruments to capture clinical data to be utilized in genotype-phenotype studies, which make comparison and collaboration studies among these researchers difficult. Objective: The purpose of this study was to develop and validate a clinical survey instrument to facilitate future collaborative genotype-phenotype studies among psoriasis genetics researchers. Methods: The Delphi method was employed to obtain international consensus on components of the novel survey instrument. The survey was pretested for acceptability purposes, and then formally tested for reliability using 3 independent raters interviewing 48 subjects with psoriasis. Results: Data showed high or moderately high agreement for questions relating to place of birth (85% to 100% in agreement), family origin (κ = 0.48 -1.0), psoriasis history (κ = 0.66-1.0), patient medical history (κ = 0.76-1.0), distribution of lesions (κ = 0.73-1.0), precipitating factors (κ = 0.79-1.0), joint involvement (κ = 0.74-.91), and treatment history, including use of oral retinoids, methotrexate, and etanercept (κ = 0.73-1.0). Other parameters had lower degrees of agreement. Limitations: The time involved and the need for the rater to be a clinician with knowledge of psoriasis may preclude widespread use of this survey instrument. Conclusion: We developed a novel, reliable survey instrument that can be used to gather clinical information in a standardized manner from psoriasis patients participating in clinical and genetics research studies.