Validation of the Dutch Quality of Life in Hand Eczema Questionnaire (QOLHEQ)

Background Measurement instruments should be validated for use in the population for which they are intended. The Quality of Life in Hand Eczema Questionnaire (QOLHEQ) has been developed to measure impairment of health-related quality of life in patients with hand eczema. Objectives To assess validity, reproducibility, responsiveness and interpretability of the Dutch version of the QOLHEQ. Methods This was a prospective validation study in adult patients with hand eczema. At three time points (T-0, baseline; T-1, after 1-3 days; T-2, after 4-12 weeks), data from the QOLHEQ and multiple reference instruments were collected. Scale structure was assessed using item response theory analysis and structural equation modelling (SEM). Single-score validity and responsiveness were tested, with hypotheses on correlations with reference instruments. Concerning reproducibility, intraclass correlation coefficients (ICCagreement) and standard error of agreement (SEMagreement) were checked. Regarding interpretability, bands for severity of quality-of-life impairment were proposed. Also, smallest detectable change (SDC) and minimally important change (MIC) were determined. Results At T-0, 300 individuals participated in the study (54% were male, mean age 45 years). Restoring of the scale structure fitted the Rasch model and the SEM. The ICCagreement, was 0.91 (95% confidence interval 0.85-0-94) and the SEMagreement was 5.2 points. Of the a priori formulated hypotheses, 80% (singlescore validity) and 64% (change scores for responsiveness) were confirmed. The SDC was 144 points and the MIC was 11.5 points. Conclusions The Dutch version of the QOLIIEQ has a good structural validity and reproducibility and has a high single-score validity and moderate responsiveness. An improvement of >= 15 points should be regarded as a real, important change within the Dutch population.