Validation of the English Version of the Kidney Disease Quality of Life Questionnaire (KDQOL-36) in Haemodialysis Patients in Singapore
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To validate a widely used health outcomes instrument for patients with chronic kidney disease and on dialysis, the Kidney Disease Quality of Life questionnaire (KDQOL-36), in English-speaking haemodialysis patients in Singapore.
This study is a secondary data analysis using the KDQOL-SF (version 1.3) data collected from a cross-sectional survey of haemodialysis patients in Singapore. Cronbach’s α was used to test internal consistency reliability. Multi-item scales were assessed using item-to-scale correlation and factor analysis. Both confirmatory and exploratory factor analyses were performed separately for generic and disease-targeted scales. Construct validity was assessed by correlation between disease-targeted and generic scales. Criterion validity was assessed by correlation of the physical component summary (PCS-12) and mental component summary (MCS-12) from KDQOL-36 with the corresponding PCS-36 and MCS-36 from the KDQOL-SF.
Three hundred ninety-four patients who completed the interviews in English [male 55.8 %, mean age (SD) 52.4 (11.7) years] were involved. Kidney disease scales exhibited desirable internal consistency (Cronbach’s α 0.822–0.906) and item-to-scale correlation (range 0.763–0.903), and a three-factor model fit the data well [comparative fit index (CFI) 0.934, root mean square error of approximation (RMSEA) 0.085]. For the generic Short Form 12 Health Survey (SF-12) items, a two-factor model (physical and mental) showed poor overall fit, but a three-factor structure (role, physical and mental functions) achieved good model fit (CFI 0.999, RMSEA 0.027). Correlation between disease-targeted and generic scales was weak to moderate (range 0.286–0.418). Correlation between SF-12 and SF-36 was 0.750 for PCS and 0.797 for MCS.
The English version of the KDQOL-36 appears to be reliable and valid to measure quality of life for haemodialysis patients in Singapore.
KeywordsExploratory Factor Analysis Haemodialysis Patient Physical Component Summary Mental Component Summary ESRD Patient
We would like to thank the Center for Health Services Research, Singapore Health Services, for sharing the data with us.
Ms. Fan Yang and Dr. Nan Luo designed the study, did the data analysis and interpretation, and drafted the manuscript. Ms. Vivian Wei Wang, Dr. Veena Joshi and Dr. Titus Lau provided intellectual content of critical importance to the paper. All authors read and approved the final manuscript.
Conflict of interest
All authors (Ms. Fan Yang, Ms. Vivian Wei Wang, Dr. Veena Joshi, Dr. Titus Lau and Dr. Nan Luo) declare that they have no competing interests.
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