Validation of the dermatology-specific proxy instrument the Infants and Toddlers Dermatology Quality of Life

Background The first dermatology-specific proxy health-related quality of life (HRQoL) instrument for children 0-4 years old with skin diseases, the Infants and Toddlers Dermatology Quality of Life (InToDermQoL), was recently developed. In order to avoid the problem of cross-cultural inequivalence focus groups work and pilot tests were organized simultaneously in all national centres of the project. The InToDermQoL showed good comprehensibility, clarity and acceptance. Objective To validate the InToDermQoL questionnaire during international field tests. Methods Internal consistency, test-retest reliability, convergent and discriminant validity of the InToDermQoL questionnaire were checked during international field tests. Results Parents of 473 children with skin diseases filled in the national language versions of the InToDermQoL questionnaire. All three age-specific versions of the InToDermQoL questionnaire with 10, 12 and 15 items, respectively, showed high internal consistency (Cronbach's alpha 0.90-0.93), good test-retest reliability (correlation coefficients > 0.9), significant correlations with the most widely used atopic dermatitis-specific proxy instrument, the Infants Dermatitis Quality of Life Index (correlation coefficients 0.68-0.79). The InToDermQoL versions for children <3 years old well correlated with the atopic dermatis severity measure Scoring of Atopic Dermatitis (correlation coefficients 0.66 and 0.86 for 10 and 12 items versions, respectively). The InToDermQoL questionnaire discriminated well among different diagnoses and disease severity levels. Conclusion Our field tests confirmed internal consistency, test-retest reliability, convergent and discriminant validity of the InToDermQoL questionnaire. Development and validation of the InToDermQoL questionnaire make it possible to assess dermatology-specific aspects of HRQoL in youngest children with skin diseases. There are many reasons to assess HRQoL in dermatologic clinical practice, and we hope that our new instrument will be used internationally in paediatric dermatology for research and practical needs.