Cross-sectional validity of the EQ-5D-Y as a generic health outcome instrument in children and adolescents with cystic fibrosis in Germany

Daniela Eidt-Koch 1 2 Thomas Mittendorf 0 2 Wolfgang Greiner 1 0 herescon gmbh , Hannover , Germany 1 Health Economics and Health Care Management, University of Bielefeld , Germany 2 Centre for Health Economics and Health System Research, Leibniz University Hannover , Germany Background: Quality of life is recognized as an important additional outcome measure in clinical trials and health economic evaluations. The EQ-5D is an important generic health outcome instrument often used for economic evaluations as a complement with disease-specific outcome measures. In this study quality of life data was assessed using the EQ-5D-Y (new EQ-5D version for children and adolescents) and the Cystic Fibrosis Questionnaire (CFQ). The objective of the study is to evaluate the cross-sectional validity of the EQ-5D-Y as a generic health outcome instrument in children and adolescents with cystic fibrosis in Germany. Methods: In 2006 a multi-centre study was conducted in four cystic fibrosis centres in Germany. Quality of life data from 96 patients between eight and seventeen years was collected using the EQ5D-Y as a generic outcome instrument and the Cystic Fibrosis Questionnaire (CFQ) as a diseasespecific instrument. Results of both instruments were compared by statistical analyses using Spearman's rank correlations. Results: 44.6% of the patients stated that they had no problems in any of the EQ-5D-Y dimensions. Several low to high correlations between separate dimensions and the visual analogue scale of the EQ-5D-Y and the different scales of the CFQ for children, their parents and adolescents can be presented in this paper. Looking at the five EQ-5D-Y dimensions the highest correlation (rS = 0.625, p = 0.01) was found between the dimension 'mobility' and the CFQ scale 'physical functioning' in adolescent patients. The overall highest correlation was found between the 'subjective health perception' and the visual analogue scale (rS = 0.744, p = 0.01) in adolescent patients older than 13 years. Conclusion: The EQ-5D-Y can be considered a cross-sectional valid generic health outcome instrument which reflects differences in health according to the progression of the life-long chronic disease cystic fibrosis. - Background Quality of life is recognized as an important additional outcome measure in clinical trials and health economic evaluations. In the past two decades many instruments for the assessment of quality of life have been developed. Most of the developed instruments for the assessment of quality of life are for adults. However, quality of life instruments for children, which are applicable in healthy as well as chronically ill children, are important and their use in clinical research should be expanded [1]. The EQ-5D is an important generic health outcome instrument often used for economic evaluations as a complement with disease-specific outcome measures. As of now, the EQ-5D is only validated for adults. Therefore the internationally applicable child friendly version EQ-5D-Y has been established by the EuroQol group and translated into many different languages (Wille N, the EuroQol Youth Task Force & Ravens-Sieberer U: Development of a child-friendly EQ-5D: the EQ-5D-Y international version, submitted). In this multi centre study quality of life data from cystic fibrosis children and adolescents was assessed using the EQ-5D-Y as a generic health outcome instrument and the Cystic Fibrosis Questionnaire (CFQ) as a disease-specific instrument in cystic fibrosis patients. Cystic fibrosis is a complex lifelong chronic disease caused by genetic mutations. In most cases multiple organ systems are affected, most patients especially suffer from pancreatic insufficiency and lung function problems. Hence, this chronic condition leads to irreversible organ damages with patients having a life expectancy of only 29 years in 2007 [2]. In this article the results of the EQ-5D-Y as well as the results of the CFQ will be analysed and correlations between dimensions and scales of the instruments will be demonstrated. The aim is to assess the cross-sectional validity of the EQ-5D-Y. Methods The multi-centre study was based on single cross-sectional data collection from children and adolescents between 8 to 17 years with cystic fibrosis in continuous ambulatory treatment in four German cystic fibrosis centres (Hannover Medical School, Johann Wolfgang Goethe University Hospital, Children's Hospital, University of Heidelberg, and the Dr. von Haunersches Kinderspital, Ludwig Maximilian University Munich) between April and August 2006. The study has been approved by the ethic committees of the involved clinics. The patients gave their consent for the study. Two instruments were used to collect quality of life data: the EQ-5D-Y as a generic health outcome instrument and the CFQ as a disease-specific instrument. The EQ-5D consists of five dimensions of health: mobility, self-care, usual activities, pain/discomfort and anxiety/ depression. The respondent can choose the levels no (1), some (2) or extreme (3) problems. The result is a health profile, e.g. a patient with the health profile 11223 has no problems with mobility and self-care, some problems with everyday activities and pain/discomfort and extreme problems with happiness/worry/sadness, respectively. The visual analogue scale (VAS) included in the EQ-5D is used to capture the patients subjective health perception between worst imaginable health state (score 0) and best imaginable health state (score 100) [3]. The EQ-5D was initially constructed and validated for adult patients. The EuroQol group now created a version for children in different languages. The EQ-5D-Y differs from the adult version in changes of words which especially were adapted for children. The German child-friendly version of the EQ5D (EQ-5D-Y) is available at the EuroQol group http:// www.euroqol.org. First studies about the child-friendly EQ-5D were presented on the 23rd Scientific Plenary Meeting of the EuroQol Group in Barcelona, Spain, September 1416, 2006 [4-10]. The Cystic Fibrosis Questionnaire (CFQ) is a disease-specific instrument for quality of life measurement in cystic fibrosis patients developed in France. Translations and validations for German language are available [11]. The CFQ has been developed in different versions for children from 8 to 13 years (CFQ-k) and their parents (CFQ-e) as well as a version for adolescents and adults aged 14 years or older (CFQ 14+). The CFQ consists of 35 (CFQ-k), 44 (CFQ-e) or 50 (CFQ 14+) items containing different modules (quality of life, general health perception, symptoms), dimensions and scales, respectively. Scales in the generic dimensions of quality of life are physical functioning, energy, emotional state, social limitations, everyday life/school problems, in the disease specific dimensions body image, eating disturbance and treatment burden. Scales for the symptoms are weight problems, respiratory and di (...truncated)