"Don't know" sign: description and evaluation of its diagnostic accuracy for cognitive impairment.

Objectives: Patients in neurology clinics are sometimes not aware of the reason for the consultation, and we have called this circumstance the "Don't know" sign (DKS). Our objective was to define this new sign and its modalities and to evaluate its prevalence and its diagnostic accuracy for cognitive impairment (CI) in comparison to other observation-based signs.

Design, Setting, And Participants: A cross-sectional prospective study included all new outpatients evaluated by the authors at neurology consultation.