Development of subscales from the symptoms/problems and effects of kidney disease scales of the kidney disease quality of life instrument

Abstract Background The Kidney Disease Quality of Life Instrument (KDQOL ™ ) was developed to provide clinicians with a comprehensive assessment of the important domains of health-related quality of life (HRQOL) for patients with end-stage renal disease who are undergoing hemodialysis. Objective The purpose of this study was to develop subscales from the 55 items comprising the Symptoms/Problems and Effects of Kidney Disease scales of the KDQOL and to measure the internal consistency reliability of these subscales. Methods The 55 items from the Symptoms/Problems and Effects of Kidney Disease scales were arranged into substantively meaningful clusters using an affinity mapping procedure. The resulting subscales were assessed for internal consistency reliability using data from a sample of 165 individuals with kidney disease who had completed the KDQOL. Results Eleven multi-item subscales were identified: pain, psychological dependency, cognitive functioning, social functioning, dialysis-related symptoms, cardiopulmonary symptoms, sleep, energy, cramps, diet, and appetite. Four items (clotting or other problems with access site, high blood pressure, numbness in hands or feet, and blurred vision) were not included in any of these subscales. Internal consistency reliability estimates for the 11 subscales ranged from 0.66 to 0.92. These subscales correlated with the scales from the 36-Item Short-Form Health Survey as hypothesized (ie, corresponding pain, energy, and social functioning scales had the highest correlations). In addition, several subscales were significantly associated, as hypothesized, with other variables such as the number of disability days. Conclusions The results of this study further support the reliability and validity of the KDQOL. The 11 subscales identified yield more detailed information on the HRQOL of patients with kidney disease and provide a basis for specific improvements in the quality of care delivered to these patients.