Analysis, evaluation and adaptation of the ReTransQoL: a specific quality of life questionnaire for renal transplant recipients.

<bold>Background: </bold>End stage renal disease (ESRD) profoundly impacts the lives of patients. Kidney transplantation provides the greatest health-related quality of life (HRQOL) improvement. Its measurement has become an important outcome parameter and a very important criterion in the evaluation of any type of medical treatment, especially in the field of renal transplantation.In 2007, a specific self-administered questionnaire for renal transplant recipients was developed in the French language: the ReTransQol (RTQ).After 5 years of use, the properties of the RTQ needed to be re-evaluated in a larger sample.This paper describes the analysis of the ReTransQol and its adaptation to achieve an improved and revised version.<bold>Methods: </bold>The study design included three analysis phases for two samples of adult renal transplant recipients which came from two cross-sectional multicenter studies carried out in France in 2007 and 2012. Psychometrics properties like construct validity, acceptability and feasibility, reliability and convergent validity were evaluated and every analysis resulted in a new version of the questionnaire: the RTQ V2. The construct validity of the new RTQ was assessed with a Confirmatory Factor Analysis on a large sample of patients.<bold>Results: </bold>The study samples included 1,059 patients and 1,591 patients, respectively. After a principal component analysis, item reduction was performed and a total of 13 items were deleted. A final version of the RTQ V2 was created and comprised of 32 items describing 5 domains: Physical Health, Social Functioning, Medical Care, Treatment and Fear of Losing Graft.The explained variance between the first and second RTQ versions improved from 46.3% to 53.1%. All psychometric properties of RTQ V2 were satisfactory: IIC >0.4, IDV (%) of 100% and Cronbach's Alpha >0.7 in every dimension. The confirmatory analysis showed that the overall scalability of the RTQ V2 was satisfactory; all items showed a good fit to the Rasch model within each dimension, and showed INFIT statistics inside the acceptable range.<bold>Conclusions: </bold>Psychometric properties allow this new version of the questionnaire to be used to assess different specific dimensions for the renal transplant population, more effectively than previously possible. [ABSTRACT FROM AUTHOR]