Self-reported skin complaints: validation of a questionnaire for population surveys

Background Estimation of skin diseases in the community is challenging because we do not easily have access to the nonhealthcare-seeking population. A potential tool is a questionnaire asking for self-reported skin complaints. Such an instrument has not yet been developed. Objectives To validate a simple instrument assessing skin morbidity in the general adult population, to predict clinical skin morbidity from self-reported skin complaints. Methods A questionnaire was drawn up in Norwegian and validated against clinical signs in two samples of an urban population, 100 healthcare-seeking adults in a dermatological clinic, and 100 nonhealthcare-seeking adults. A total self-reported score was calculated and validated against severity of clinical signs (no sign, trivial, moderate or severe). The inter-rater agreement was assessed in a small study including 16 patients from a dermatological clinic. Results The participation rate was 98%. The sensitivity was 61%, the specificity 69% and the positive predictive value 82% when the caseness criterion was any clinical sign of skin disease. The agreement was good between the two observers for clinical skin morbidity, with kappa = 0.67. Conclusions This questionnaire is a simple tool to evaluate skin morbidity in an adult population. The use of self-reported complaints to predict clinical morbidity may be of value in quantifying and exploring skin diseases at the population level. Further studies are needed to improve the instrument. It is our intention to demonstrate the potential usefulness of this questionnaire in a forthcoming population survey in Norway