Background The epidemiology of atopic dermatitis (AD) in the U.S.A. has been described largely via US population-based questionnaire studies. However, the validity of the questions used for self- and caregiver-reported eczema has not been previously demonstrated. Objectives To validate the assessment of self- and caregiver-reported eczema. Methods We performed a prospective multicentre dermatology-practice-based study (three sites) to determine the validity of caregiver- and self-reported ever having eczema and 1-year history of eczema. Questionnaires were administered to unselected patients prior to their encounter. Patients (n = 782) were then evaluated by expert dermatologists trained in utilizing the Hanifin and Rajka criteria for AD. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value were determined. Results Caregiver-reported 1-year history of childhood eczema was found to have a sensitivity (95% confidence interval) of 0·70 (0·59-0·80), specificity of 0·96 (0·93-0·99) and PPV of 0·87 (0·78-0·96) when compared with a physician's diagnosis of AD at that visit. Similarly, self-reported 1-year history of adult eczema was found to have a sensitivity of 0·70 (0·59-0·80), specificity of 0·95 (0·93-0·97) and PPV of 0·76 (0·64-0·85). The specificities and PPVs of a history of ever having caregiver- (0·89, 0·82-0·96 and 0·81, 0·70-0·93) and self-reported eczema (0·97, 0·95-0·99 and 0·91, 0·85-0·97) were high, with a high sensitivity in children (0·83, 0·72-0·95) but not in adults (0·43, 0·37-0·51). Conclusions Self- and caregiver-reported diagnosis of eczema ever or in the past year based on a single question demonstrates sufficient validity for the epidemiological study of AD.
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