Quality of life in children and adolescents with cystic fibrosis: implications for optimizing treatments and clinical trial design

Health related quality of life (QOL) as an outcome measure in clinical trials is becoming increasingly important. Trials should not only be able to demonstrate the pharmacologic activity of a therapy, but of equal importance, they should demonstrate clinical effectiveness that is of significant benefit to the patient. QOL measurement provides a way of incorporating the child/parent's perspective of how cystic fibrosis (CF) and its therapies impact on their lives. Several validated generic instruments have been employed to measure QOL in adolescents and adults. QOL assessment is more difficult in children and, therefore, has been employed less often in children with CF. Difficulties arise with the issue of whether children can report their own experiences directly, or whether a parent or clinician should report on behalf of the child. A child-centered approach is imperative since the literature indicates that children are able to report on their own QOL. An additional complication has been the use of adult measures with children. These are often inappropriate in their complexity, use of language, response scales, and time frame. The evaluation of pharmacologic therapies can profit from QOL measurement. The effectiveness of a drug and any adverse effects that impact on daily life can be assessed from the child/parent's viewpoint. Home therapy versus hospital therapy and drug delivery systems, are additional areas where QOL as an outcome measure is valuable. There have been relatively few appropriately powered trials in CF, and only a minority of these have evaluated QOL as an outcome measure. This review highlights areas where QOL measurement is appropriate. It focuses on the pharmacologic trials that have employed QOL assessment for antibiotic, mucociliary clearance, anti-inflammatory, and nutritional therapies. Methodological issues of incorporating QOL assessment into trials center on cross-cultural and data interpretation issues. QOL measurement in CF has been patchy and largely unreliable. The notion that improved symptoms equate with improved QOL is erroneous. Measurement of how symptoms impact on QOL is essential. Currently, the development and validation of CF specific measures (across the CF age range) provides optimism for appropriate QOL measurement in clinical trials, and for future meta-analysis and systematic reviews.