Association of Digital Clock Drawing with PET Amyloid and Tau Pathology in Normal Older Adults
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Abstract
Objective: To determine whether a digital clock drawing test, DCTclock™, improves upon standard cognitive assessments for discriminating diagnostic groups and for detecting biomarker evidence of amyloid and tau pathology in clinically normal older adults (CN).
Methods: Participants from the Harvard Aging Brain Study and the Positron Emission Tomography (PET) lab at Massachusetts General Hospital were recruited to undergo the DCTclock drawing test, standard neuropsychological assessments including the Preclinical Alzheimer Cognitive Composite (PACC), and amyloid /tau PET imaging. Receiver operating curve analyses were used to assess diagnostic and biomarker discriminability. Logistic regression and partial correlations were used to assess DCTclock performance in relation to PACC and PET biomarkers.
Results: A total of 300 participants were studied. Among the 264 CN, 143 had amyloid and tau PET imaging (Clinical Dementia Rating=0, Mini Mental State Exam=28.9±1.2). An additional 36 participants with a diagnosis of mild cognitive impairment or early Alzheimer’s dementia (CDR=0.5, MMSE=25.2±3.9) were added to assess diagnostic discriminability. DCTclock showed excellent discrimination between diagnostic groups (AUC=0.86). Among CN with biomarkers, the DCTclock summary score and spatial reasoning sub-scores were associated with greater amyloid and tau burden and showed better discrimination (Cohen’s d=0.76) between Aβ+/- groups than the PACC (d=0.30).
Conclusion: DCTclock discriminates between diagnostic groups and improves upon traditional cognitive tests for detecting biomarkers of amyloid and tau pathology in CN older adults. The validation of such digitized measures has the potential of providing an efficient tool for detecting early cognitive changes along the AD trajectory.
Classification of Evidence: This study provides Class II evidence that the DCTclock results were associated with amyloid and tau burden in clinically normal older adults.
- Received May 9, 2020.
- Accepted in final form December 30, 2020.
- © 2021 American Academy of Neurology
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