Objective: The international development of the Parents' Index of Quality of Life in Atopic Dermatitis (PIQoL-AD), a quality of life (QoL) instrument specific to parents of children with atopic dermatitis (AD) is described.
Method: The instrument was developed simultaneously in several countries. Its content was derived from 65 qualitative interviews with parents in the UK, Netherlands and Italy. The measure was then produced for the UK, Netherlands, Italy, Germany, France, US and Spain. Field-test interviews were conducted with approximately 20 patients in each country to assess face and content validity. A two time-point survey was conducted with between 45 and 328 parents in each country to finalise the instrument through application of the Rasch model and to evaluate the psychometric properties of the final instrument.
Results: Application of the Rasch model to the survey data identified the final 28-item version. All language versions had good item fit, test-retest reliability (above 0.85), internal consistency and promising validity.
Conclusions: The PIQoL-AD is a valuable instrument for inclusion in clinical trials and routine clinical practice. It provides distinct and complementary information to that of existing dermatology-specific measures and has been shown to be responsive to changes in QoL in clinical trials.