Validation of the Kidney Disease Quality of Life (KDQOL) cognitive function subscale.
BACKGROUND
Formal cognitive function testing is cumbersome, and no self-administered instruments for estimating cognitive function in persons with chronic kidney disease (CKD) and end-stage renal disease (ESRD) have been validated. The goal of this study was to determine the validity of the Kidney Disease Quality of Life Cognitive Function scale (KDQOL-CF) for the assessment of cognitive impairment in persons with kidney disease.


METHODS
We administered the KDQOL-CF to 157 subjects, 79 with ESRD and 78 with CKD participating in a cross-sectional study of cognitive function. Scores on the Modified Mini-Mental State Exam (3MS) were considered the gold standard measure of global cognitive function. Performance characteristics of the KDQOL-CF were assessed using correlation coefficients, Bland-Altman plots, and receiver operating characteristic curves.


RESULTS
Median scores on the KDQOL-CF were 73 (interquartile range 60-87) for subjects with ESRD and 87 (interquartile range 73-100) for subjects with CKD (P < 0.0001). Scores on the KDQOL-CF were directly correlated with scores on the 3MS (r = 0.31, P = 0.0001). Defining global cognitive impairment as a 3MS score < 80, a cut-point of 60 on the KDQOL-CF accurately classified 76% of subjects, with 52% sensitivity and 81% specificity. On multivariable analysis, cerebral and peripheral vascular disease, benzodiazepine use, and higher serum phosphorus concentrations were associated with lower KDQOL-CF scores, while beta blocker use, education, and higher serum albumin concentrations were associated with higher KDQOL-CF scores.


CONCLUSIONS
The KDQOL-CF is a valid instrument for estimating cognitive function in patients with CKD and ESRD. KDQOL-CF screening followed by 3MS testing in selected individuals may prove to be an effective and efficient strategy for identifying cognitive impairment in patients with kidney disease.
Kurella
Manjula
M
Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California 94118-1211, USA.
Luan
Jennifer
J
Yaffe
Kristine
K
Chertow
Glenn M
GM
D000368:Aged; D003072:Cognition Disorders / Q000175:diagnosis* / Q000523:psychology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011237:Predictive Value of Tests; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*