Using Base Rate of Low Scores to Identify Progression from Amnestic Mild Cognitive Impairment to Alzheimer's Disease.

To investigate the implications of obtaining one or more low scores on a battery of cognitive tests on diagnosing mild cognitive impairment (MCI). Observational longitudinal study. Alzheimer's Disease Neuroimaging Initiative. Normal controls (NC, n = 280) and participants with MCI (n = 415) according to Petersen criteria were reclassified using the Jak/Bondi criteria and number of impaired tests (NIT) criteria. Diagnostic statistics and hazard ratios of progression to Alzheimer's disease (AD) were compared according to diagnostic criteria. The NIT criteria were a better predictor of progression to AD than the Petersen or Jak/Bondi criteria, with optimal sensitivity, specificity, and positive and negative predictive value. Considering normal variability in cognitive test performance when diagnosing MCI may help identify individuals at greatest risk of progression to AD with greater certainty.