The Kidney Disease Quality of Life Cognitive Function Subscale and Cognitive Performance in Maintenance Hemodialysis Patients

Background: Cognitive impairment is common but often undiagnosed in patients with end-stage renal disease, in part reflecting limited validated and easily administered tools to assess cognitive function in dialysis patients. Accordingly, we assessed the utility of the Kidney Disease Quality of Life Cognitive Function (KDQOL-CF) scale in comparison to an extensive neuropsychological battery, building on a prior assessment of this potential cognitive screen. Study Design: Cross-sectional cohort. Setting & Participants: Maintenance hemodialysis patients at 6 Boston area dialysis units were administered an extensive neurocognitive battery and the KDQOL-CF at the beginning of a hemodialysis session. Predictors: KDQOL-CF score, depression symptom burden, and demographic and clinical characteristics. Outcomes: Neurocognitive performance classified into executive function and memory domains, determined using principal components analysis. Measurements: Univariate and multivariable linear regression models adjusting for age, sex, race, and end-stage renal disease cause were used to evaluate the association between KDQOL-CF score and cognitive performance, and test metrics were determined for a KDQOL-CF cutoff score of 60 or less from a maximum score of 100. Results: For 168 prevalent hemodialysis patients, KDQOL-CF score was 76 +/- 19 and 40 (24%) had scores of 60 or less, consistent with self-identified worse cognitive performance. There was no significant correlation between KDQOL-CF score and either memory (P = 0.2 and P = 0.3) or executive function (P = 0.1 and P = 0.4) in univariate and multivariable models, respectively. There was a strong correlation between higher KDQOL-CF score and fewer depression symptoms (P < 0.001). Sensitivity of the KDQOL-CF was poor (range, 0.28-0.36), with modest specificity (range, 0.77-0.81) for identifying worse executive function and memory. Limitations: Cross-sectional study, modest population size, and abbreviated gold-standard cognitive battery. Conclusions: The KDQOL-CF is a poor determinant of neurocognitive performance in hemodialysis patients, with limited sensitivity. To assess cognitive impairment in hemodialysis patients, better screening tests are essential. Am J Kidney Dis. 60(3): 417-426. (C) 2012 by the National Kidney Foundation, Inc.