In their interesting article, Klatka and coworkers1 present neuropathological data on a group of 170 patients clinically diagnosed as having Alzheimer disease (AD), including 93 prospective and 77 retrospective cases. Of these 170 patients, 149 met histopathological criteria for AD, with similar numbers for prospectively or retrospectively studied patients. There were 21 patients who received other histopathological diagnoses than AD. The authors sought to describe the clinical characteristics that might give clues to consider an alternative diagnosis, what they call red flags.
Five red flags are presented in this study that include parkinsonian features, absence of language impairment, absence of visuospatial impairment, early personality change, and focal neurological signs. For a red flag to have clinical relevance in identifying patients without AD, the ratio of the proportion of patients without AD with a red flag (true-positives) relative to the proportion of patients with AD also having a red flag