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

Background: The Kidney Disease Quality of Life Instrument (KDQOL(TM)) was d eveloped to provide clinicians with a comprehensive assessment of the impor tant domains of health-related quality of life (HRQOL) for patients with en d-stage renal disease who are undergoing hemodialysis. Objective: The purpose of this study was to develop subscales from the 55 i tems comprising the Symptoms/Problems and Effects of Kidney Disease scales of the KDQOL and to measure the internal consistency reliability of these s ubscales. Methods: The 55 items from the Symptoms/Problems and Effects of Kidney Dise ase scales were arranged into substantively meaningful clusters using an af finity mapping procedure. The resulting subscales were assessed for interna l 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 d ependency, cognitive functioning, social functioning, dialysis-related symp toms, cardiopulmonary symptoms, sleep, energy, cramps, diet, and appetite. Four items (clotting or other problems with access site, high blood pressur e, numbness in hands or feet, and blurred vision) were not included in any of these subscales. Internal consistency reliability estimates for the 11 s ubscales ranged from 0.66 to 0.92. These subscales correlated with the scal es from the 36-Item Short-farm Health Survey as hypothesized tie, correspon ding pain, energy, and social functioning scales had the highest correlatio ns). In addition, several subscales were significantly associated, as hypot hesized, 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 info rmation on the HRQOL of patients with kidney disease and provide a basis fo r specific improvements in the quality of care delivered to these patients.