Evaluation of Screening Tests for Cognitive Impairment in Patients Receiving Maintenance Hemodialysis

Significance Statement Cognitive impairment is common among individuals receiving maintenance hemodialysis, but few data exist regarding how well screening tests for cognitive function perform in this population. The authors assessed the ability of the Mini Mental State Examination, the Modified Mini Mental State Examination, the Montreal Cognitive Assessment, the Trail Making Test Part B, the Mini-Cog test, and the Digit Symbol Substitution Test to predict severe cognitive impairment in a cohort of 150 patients on dialysis whose cognitive status had been first defined with a battery of neurocognitive tests. The Montreal Cognitive Assessment was the best-performing overall screening test, and the authors recommend it as the preferred test to screen for severe cognitive impairment in patients receiving maintenance hemodialysis. Identification of such impairment may then facilitate optimal medical management and discussion of relevant issues with patients and family members. Background Neurocognitive testing shows that cognitive impairment is common among patients receiving maintenance hemodialysis. Identification of a well performing screening test for cognitive impairment might allow for broader assessment in dialysis facilities and thus optimal delivery of education and medical management. Methods From 2015 to 2018, in a cohort of 150 patients on hemodialysis, we performed a set of comprehensive neurocognitive tests that included the cognitive domains of memory, attention, and executive function to classify whether participants had normal cognitive function versus mild, moderate, or severe cognitive impairment. Using area-under-the-curve (AUC) analysis, we then examined the predictive ability of the Mini Mental State Examination, the Modified Mini Mental State Examination, the Montreal Cognitive Assessment, the Trail Making Test Part B, the Mini-Cog test, and the Digit Symbol Substitution Test, determining each test’s performance for identifying severe cognitive impairment. Results Mean age was 64 years; 61% were men, 39% were black, and 94% had at least a high-school education. Of the 150 participants, 21% had normal cognitive function, 17% had mild cognitive impairment, 33% had moderate impairment, and 29% had severe impairment. The Montreal Cognitive Assessment had the highest overall predictive ability for severe cognitive impairment (AUC, 0.81); a score of ≤21 had a sensitivity of 86% and specificity of 55% for severe impairment, with a negative predictive value of 91%. The Trails B and Digit Symbol tests also performed reasonably well (AUCs, 0.73 and 0.78, respectively). The other tests had lower predictive performances. Conclusions The Montreal Cognitive Assessment, a widely available and brief cognitive screening tool, showed high sensitivity and moderate specificity in detecting severe cognitive impairment in patients on maintenance hemodialysis.