Value of neuropsychological tests, neuroimaging, and biomarkers for diagnosing Alzheimer's disease in younger and older age cohorts.

OBJECTIVES

To examine the influence of age on the value of four techniques for diagnosing Alzheimer's disease (AD).

DESIGN

Observational cohort study.

SETTING

Alzheimer's Disease Neuroimaging Initiative.

PARTICIPANTS

Individuals with mild cognitive impairment (MCI; n = 179), individuals with AD (n = 91), and normal controls (n = 105).

MEASUREMENTS

Neuropsychological tests, structural magnetic resonance imaging (MRI), amyloid-beta and tau in cerebrospinal fluid (CSF), and [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) for the diagnosis of MCI or AD. MCI was defined according to subjective memory complaints corroborated by an informant and an abnormal score on the delayed paragraph recall subtest of the Wechsler Memory Scale-Revised, a Mini-Mental State Examination score greater than 23, and a Clinical Dementia Rating score of 0.5. Participants with AD satisfied National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association criteria of probable AD.

RESULTS

Neuropsychological tests and MRI were the most informative techniques, with 84% and 82% correct classifications, respectively, and areas under the receiver operating characteristic curve (AUCs) of 0.93 (90% confidence interval (CI) = 0.91-0.95) and 0.88 (90% CI = 0.85-0.91). FDG-PET and CSF assessments had 76% and 73% correct classifications, respectively, (AUC = 0.77, 90% CI = 0.71-0.83; AUC = 0.77, 90% CI = 0.73-0.82). These figures increased slightly when the techniques were combined. All analyses were repeated for the younger (<75) and older (≥ 75) halves of the sample. FDG-PET and CSF assessment were substantially less informative in the older cohort, and they did not add diagnostic information when all techniques were combined.

CONCLUSIONS

Structural MRI and neuropsychological assessment are diagnostic methods of first choice if AD is suspected. CSF and FDG-PET add little to these diagnostic techniques, especially in older adults.