The quality of life of parents of children with atopic dermatitis: interpretation of PIQoL-AD scores.

The PIQoL-AD has been used in several trials assessing quality of life (QoL) in parents of children with atopic dermatitis (AD), treated with pimecrolimus cream 1%. Secondary analysis of data from four trials (n = 621) was undertaken to help interpret the meaningfulness (significance) of the QoL results. A combination of anchor-based and distribution-based methods of interpreting instrument scores were employed. For each level on four AD severity indicators, mean PIQoL-AD scores and 95% confidence intervals were calculated. Low levels of association (r(s) range = 0.12-0.45) were observed between QoL and clinical indicators; confirming previous findings. When data from the different trials and time-points were combined clear patterns emerged indicating the clinical meaning of PIQoL-AD scores. Distribution-based statistics such as effect sizes, the standard error of measurement (SEM) and the standard error of difference (S(diff)) were also calculated. Despite a lack of consensus on how best to determine the meaningfulness of QoL scores, a large database of trial data was successfully used to link QoL scores to disease severity, aiding clinical interpretation of the former. Effect size, SEM and S(diff) values were consistent across the trials indicating that a change of 2 to 3 PIQoL-AD points over time could be considered meaningful. It is argued that it would be useful for clinicians to gain an understanding of the meaning of QoL scores through routine use of such measures in clinical practice.