Detecting delirium among hospitalized older patients.

BACKGROUND: Delirium occurs commonly among older hospitalized patients and is frequently not recognized. In an effort to identify tools useful to clinicians in the diagnosis of delirium, test characteristics of four screening instruments were compared.
METHODS: Patients 65 years of age or older who were admitted to one of four medical and surgical wards of a university teaching hospital were followed up prospectively. Potential subjects were excluded if unavailable for interviews or discharged within 48 hours of admission, or if judged too impaired to participate in the daily interviews. Research assistants administered four instruments used to detect delirium: Digit Span Test, Vigilance 'A' Test, Clinical Assessment of Confusion, and Confusion Assessment Method. Abnormal scores on these tests or suspicion of acute confusion prompted a referral to the clinician-investigators who then assessed the patient daily for delirium based on the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition criteria.
RESULTS: Delirium occurred in 64 (14.8%) of 432 subjects. The positive likelihood ratios for all of the instruments were significantly more than 1. The instruments remained useful when applied to selected subgroups: subjects in whom acute mental status changes were documented, subjects on surgical services, and subjects with impaired cognitive status on admission. Combinations of any two instruments did not perform substantially better than the instrument with the best test characteristics: the Clinical Assessment of Confusion. All instruments were more useful at confirming delirium than in excluding it.
CONCLUSION: The four instruments studied, which are suitable for use at the bedside, can aid the clinician in identifying patients likely to be suffering from delirium.