Adaptation and validation of the Spanish version of "Kidney Disease Questionnaire"

The objective of this study was to adapt and validate the Kidney Disease Questionnaire (KDQ) for use in Spain. The KDQ is a disease-specific health-related quality of life questionnaire for patients receiving hemodialysis. The original english version was translated and back translated by bilingual translators and the preliminary Spanish version was then tested in 10 hemodialysis patients to assess patient comprehension and its feasibility for use in a Spanish-speaking population. The list of symptoms in this initial version was then revised by 25 doctors and nurses specialising in hemodialysis, who reorder-ed the symptoms in accordance with their frequency and importance. The preliminary validity and reliability of the Spanish version were assesed in 35 patients receiving long-term hemodialysis. The first phase consisted of administering the KDQ together with an assessment of self-rated health and the Spanish versions of the EuroQol questionnaire and the Sickness Impact Profile. Two weeks after initial administration of the questionnaire, patients were required to answer a question on changes in their health status, as well as being asked to complete the KDQ and the EuroQol for a second time. The Spanish version of the KDQ showed high internal consistency, with a Cronbach's alpha for each dimension ranging between 0.67 and 0.87, and for the questionnaire as a whole of 0.93. No differences were found in the mean values obtained during the initial and follow-up administrations of the KDQ, whilst the intraclass correlation coefficient varied between 0.62 and 0.77. The Spanish version of the KDQ showed acceptable levels of correlation with other measures of self-rated health, with coefficients between -0.45 and -0.83 with the dimensions and overall score of the SIP (higher than those obtained in the validation of the original English version), and between 0.39 and 0.65 with the EuroQol tariff values and thermometer. The similarity of these opera ting characteristics supports the contention that the Spanish and English versions of the KDQ are conceptually equivalent. Nevertheless, before accepting that the two versions are completely equivalent, it will be necessary to test this version on a larger sample, to revise and modify the list of symptoms in a large group of hemodialysis patients, and to evaluate other spychometric properties such as sensitivity to change in health status.