Construct validity of the questionnaire on experience with skin complaints (short form) - Identification of a subscale responsive to physical treatment

Introduction: Feelings of stigmatization can strongly influence quality of life in individuals with chronic skin diseases. The Short-Form of the Questionnaire on Experience with Skin Complaints (SF-QES) differentiates four factors of stigmatization: self-esteem and retreat, experienced refusal, concealment, and composure. The current study aimed to investigate the construct validity of the SF-QES. Method: The analysis was based on the complete SF-QES records of a clinical psoriasis trial, which yielded 1,005 records at baseline, 1,010 records at the end of therapy, and 885 and 827 records, respectively, at two follow-ups. Factor analyses and corresponding structural equation models (SEMs) using robust maximum likelihood estimation (RML) were applied. Additionally, the responsiveness of the scales to judgments of treatment success and two different interventions were compared. Results: The factor analyses provided results that widely agreed with the supposed four factors. SEM, however, showed moderately insufficient fit for this model, but supported five factors and the discrimination between affected self-esteem and retreat. The retreat scale was clearly most responsive to treatment success and intervention type. Conclusion: The construct validity of the SF-QES was largely supported, but the factor retreat should be separated from affected self-esteem and is most sensitive to physical intervention.