Accuracy of Biomarker Testing for Neuropathologically Defined Alzheimer Disease in Older Adults With Dementia.

BACKGROUND: Biomarker accuracy for Alzheimer disease (AD) is uncertain. PURPOSE: To summarize evidence on biomarker accuracy for classifying AD in older adults with dementia. DATA SOURCES: Electronic bibliographic databases (searched from January 2012 to November 2019 for brain imaging and cerebrospinal fluid [CSF] tests and from inception to November 2019 for blood tests), ClinicalTrials.gov (to November 2019), and systematic review bibliographies. STUDY SELECTION: English-language studies evaluating the accuracy of brain imaging, CSF testing, or blood tests for distinguishing neuropathologically defined AD from non-AD among older adults with dementia. Studies with low or medium risk of bias were analyzed. DATA EXTRACTION: Two reviewers rated risk of bias. One extracted data; the other verified accuracy. DATA SYNTHESIS: Fifteen brain imaging studies and 9 CSF studies met analysis criteria. Median sensitivity and specificity, respectively, were 0.91 and 0.92 for amyloid positron emission tomography (PET), 0.89 and 0.74 for 18F-labeled fluorodeoxyglucose (18F-FDG) PET, 0.64 and 0.83 for single-photon emission computed tomography, and 0.91 and 0.89 for medial temporal lobe atrophy on magnetic resonance imaging (MRI). Individual CSF biomarkers and ratios had moderate sensitivity (range, 0.62 to 0.83) and specificity (range, 0.53 to 0.69); in the few direct comparisons, ß-amyloid 42 (Aß42)/phosphorylated tau (p-tau) ratio, total tau (t-tau)/Aß42 ratio, and p-tau appeared more accurate than Aß42 and t-tau alone. Single studies suggested that amyloid PET, 18F-FDG PET, and CSF test combinations may add accuracy to clinical evaluation. LIMITATIONS: Studies were small, biomarker cut points and neuropathologic AD were inconsistently defined, and methods with uncertain applicability to typical clinical settings were used. Few studies directly compared biomarkers, assessed test combinations, evaluated whether biomarkers improved classification accuracy when added to clinical evaluation, or reported harms. CONCLUSION: In methodologically heterogeneous studies of uncertain applicability to typical clinical settings, amyloid PET, 18F-FDG PET, and MRI were highly sensitive for neuropathologic AD. Amyloid PET, 18F-FDG PET, and CSF test combinations may add accuracy to clinical evaluation. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality. (PROSPERO: CRD42018117897).

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

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).

Benefits and Harms of Prescription Drugs and Supplements for Treatment of Clinical Alzheimer-Type Dementia.

BACKGROUND: Effects of drug treatment of clinical Alzheimer-type dementia (CATD) are uncertain. PURPOSE: To summarize evidence on the effects of prescription drugs and supplements for CATD treatment. DATA SOURCES: Electronic bibliographic databases (inception to November 2019), ClinicalTrials.gov (to November 2019), and systematic review bibliographies. STUDY SELECTION: English-language trials of prescription drug and supplement treatment in older adults with CATD that report cognition, function, global measures, behavioral and psychological symptoms of dementia (BPSD), or harms. Minimum treatment was 24 weeks (≥2 weeks for selected BPSD). DATA EXTRACTION: Studies with low or medium risk of bias (ROB) were analyzed. Two reviewers rated ROB. One reviewer extracted data; another verified extraction accuracy. DATA SYNTHESIS: Fifty-five studies reporting non-BPSD outcomes (most ≤26 weeks) and 12 reporting BPSD (most ≤12 weeks) were analyzed. Across CATD severity, mostly low-strength evidence suggested that, compared with placebo, cholinesterase inhibitors produced small average improvements in cognition (median standardized mean difference [SMD], 0.30 [range, 0.24 to 0.52]), no difference to small improvement in function (median SMD, 0.19 [range, -0.10 to 0.22]), no difference in the likelihood of at least moderate improvement in global clinical impression (median absolute risk difference, 4% [range, 2% to 4%]), and increased withdrawals due to adverse events. In adults with moderate to severe CATD receiving cholinesterase inhibitors, low- to insufficient-strength evidence suggested that, compared with placebo, add-on memantine inconsistently improved cognition and improved global clinical impression but not function. Evidence was mostly insufficient about prescription drugs for BPSD and about supplements for all outcomes. LIMITATION: Most drugs had few trials without high ROB, especially for supplements, active drug comparisons, BPSD, and longer trials. CONCLUSION: Cholinesterase inhibitors and memantine slightly reduced short-term cognitive decline, and cholinesterase inhibitors slightly reduced reported functional decline, but differences versus placebo were of uncertain clinical importance. Evidence was mostly insufficient on drug treatment of BPSD and on supplements for all outcomes. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality. (PROSPERO: CRD42018117897).