Is the kidney disease quality of life-36 (KDQOL-36) a valid instrument for Chinese dialysis patients?

BACKGROUND The aim of this study is to determine the validity and reliability of the Cantonese Chinese version of the Kidney Disease Quality of Life-36 (KDQOL-36™) questionnaire. The scale has been translated into Cantonese Chinese, but has not been tested among the Cantonese-speaking populations. METHODS A total of 110 dialysis patients and 122 renal transplant patients were recruited. The data for the KDQOL-36™ were extracted from the KDQOL-Short Form. The criterion validity and scale equivalence were examined using the KDQOL-Short Form scores as the gold standard. The Hospital Anxiety and Depression scale was used to identify the correlations between depression, anxiety, and quality of life to establish the convergent validity. Discriminant validity was examined using the transplant patients to compare the quality of life of dialysis patients. The Cronbach's alpha coefficient and test-retest were used for estimating reliability. RESULTS There were very strong positive correlations for the physical and mental component summary between the KDQOL-36™ and KDQOL-Short Form. Despite the strong correlations, the effect size was 0.6 and 0.13 for the physical composite summary and mental composite summary score, respectively. Most of the subscales demonstrated significant moderate correlations with the Hospital Anxiety and Depression Scale, from -0.265 to -0.516. The discriminant validity was confirmed with a significant difference between the dialysis and transplant group patients. A high intraclass correlation of >0.98 was demonstrated in the test-retest. CONCLUSION The Cantonese Chinese KDQOL-36™ was reliable. Further testing will be required to determine its validity for the physical health summary scale.