Validity of self-reports of hand eczema

The validity of questionnaire answers with respect to hand eczema was investigated. Car mechanics, dentists and office workers answered a questionnaire on the occurrence of hand eczema on any occasion during the past 12 months. Yes-responders and a random sample of no-responders were subsequently interviewed and examined by a dermatologist. 10.0% of the car mechanics, 12.0% of the dentists and 12.5% of the office workers were found to have hand eczema despite previous no-answers. In the same populations, 81%, 94% and 80% of the yes-answers were confirmed at the clinical examination. Considering false-negative and false-positive answers, the sensitivity was 53-59% and the specificity 96-99% in the 3 groups. The 1-year prevalence changed from self-reported 15% to estimated 21% in the car mechanics, from 15% to 24% in the dentists and from 15% to 23% in the office workers. It is concluded that self-reported 1-year prevalence of hand eczema considerably underestimates the true prevalence.