Delirium in hospitalized patients is most closely associated with factors already present on admission such as prior cognitive impairment, advanced age, and fracture. In the hospital, use of neuroleptics and narcotics and the presence of infection are less strongly associated with this syndrome.

To study delirium in hospitalized elderly, a delirium symptom interview (DSI) was developed by an interdisciplinary group of investigators. This interview was administered in an acute care hospital to 50 patients who were over the age of 65 years. Results from the interview were compared to assessments of major symptoms of delirium made independently by a neurologist and a psychiatrist. This interview had good validity and reliability. The sensitivity of the DSI was .90 and the specificity was .80, when compared with the clinical judgment of a psychiatrist and neurologist. Interrater reliability, using lay interviewers, was .90 for the detection of major symptoms of delirium. These results indicate that the DSI could be used by lay interviewers to assess reliably the symptoms of delirium.

Over the past several decades, numerous investigators have studied the syndrome of delirium. Researchers have relied on a number of different case finding methods to detect the syndrome. This paper provides an overview of instruments used in studies of delirium. We assess the validity and reliability of these instruments and compare the advantages and disadvantages of the different methods. We then present the rationale for the development of the Delirium Symptom Interview, an instrument constructed for use in the Commonwealth-Harvard Study of delirium in elderly hospitalized patients.

The development of new criteria for delirium (e.g., DSM-IV) will have to balance the need to define a pure group of patients for research purposes with the need to include cases of clinical interest. Changes in criteria should be based on data such as those presented in this paper.

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