Relationship between dialysis adequacy and quality of life in long-term peritoneal dialysis patients

Objective: The purpose of this study was to compare quality of life (QOL) between peritoneal dialysis (PD) patients with adequate and inadequate total solute clearance (TSC). We also tried to determine the relationship between QOL and TSC. Design: A cross-sectional study design was used in which QOL was evaluated and compared between PD patients with adequate and inadequate TSC. Setting: The PD unit of a university teaching hospital. Patients: Sixty-seven patients were recruited, 38 on continuous ambulatory PD and 29 on continuous cycler-assisted PD. Methods: Patients were divided into adequate and inadequate groups, based on the results of either total urea clearance (Kt/V(urea)) or total creatinine clearance (weekly CCr). The demographic data, dialysis variables, and clinical parameters of these patients were all collected. QOL was evaluated using the SF-36 questionnaire, which contains eight domains and is a comprehensive and validated instrument for QOL evaluation. QOL of patients in adequate and inadequate groups was compared. The relationship between QOL and TSC was also examined. Results: Among patients grouped by Kt/V(urea), patients in the adequate group had significantly higher scores in two domains of the SF-36, that is, physical and emotional role functioning, than did those in the inadequate group. The total SF-36 scores were positively correlated with Kt/V(urea) when all patients were pooled together. However, among patients grouped by weekly CCr, there was no significant difference in any of the eight domains of the SF-36 between patients in the adequate and inadequate groups. No correlation was found between the total SF-36 scores and weekly CCr. Conclusion: Our study had two important findings: First, PD patients with adequate total solute clearance, based on Kt/V(urea) and not on weekly CCr, had a better QOL. Second, Kt/V(urea) is better correlated with QOL than weekly CCr. These findings suggest that Kt/V(urea) is a better parameter for the clinical evaluation of total solute clearance from the viewpoint of QOL.