Brief Cognitive Tests for Distinguishing Clinical Alzheimer-Type Dementia From Mild Cognitive Impairment or Normal Cognition in Older Adults With Suspected Cognitive Impairment

Abstract

Background: The accuracy and harms of brief cognitive tests for identifying clinical Alzheimer-type dementia (CATD) are uncertain.

Purpose: To summarize evidence on accuracy and harms of brief cognitive tests for CATD in older adults with suspected cognitive impairment.

Data sources: Electronic bibliographic databases (from inception to November 2019) and systematic review bibliographies.

Study selection: English-language, controlled observational studies in older adults that evaluated the accuracy of brief cognitive tests (standalone tests; memory, executive function, and language tests; and brief multidomain batteries) for distinguishing CATD from mild cognitive impairment (MCI) or normal cognition as defined by established diagnostic criteria. Studies with low or medium risk of bias (ROB) were analyzed.

Data extraction: Two reviewers rated ROB. One reviewer extracted data; the other verified extraction accuracy.

Data synthesis: Fifty-seven studies met analysis criteria. Many brief, single cognitive tests were highly sensitive and specific for distinguishing CATD from normal cognition. These included standalone tests (clock-drawing test, median sensitivity 0.79 and specificity 0.88 [8 studies]; Mini-Mental State Examination, 0.88 and 0.94 [7 studies]; Montreal Cognitive Assessment, 0.94 and 0.94 [2 studies]; and Brief Alzheimer Screen, 0.92 and 0.97 [1 study]), memory tests (list delayed recall, 0.89 and 0.94 [5 studies]), and language tests (category fluency, 0.92 and 0.89 [9 studies]). Accuracy was lower in distinguishing mild CATD from normal cognition and distinguishing CATD from MCI. No studies reported on testing harms.

Limitations: Studies were small. Few test metrics were evaluated by multiple studies. Few studies directly compared different tests, scores, cut points, or test combinations.

Conclusion: Many brief, single cognitive tests accurately distinguish CATD from normal cognition in older adults but are less accurate in distinguishing mild CATD from normal cognition or CATD from MCI. No studies reported on testing harms.

Primary funding source: Agency for Healthcare Research and Quality. (PROSPERO: CRD42018117897).

Keywords: Cognition; Cognitive impairment; Cohort studies; Dementia; Elderly; Longitudinal studies; Memory recall; Retrospective studies; Sensitivity; Specificity.