Evidence for the Diagnostic Criteria of Delirium

An Update

Dan G. Blazer; Adrienne O. van Nieuwenhuizen


Curr Opin Psychiatry. 2012;25(3):239-243. 

In This Article

Subsyndromal Delirium

By definition, delirium develops over a short period (usually hours to a few days) and represents an acute change from the baseline cognitive status of the patient that is not solely attributable to another cognitive disorder (such as a stroke); it also tends to fluctuate in severity during the course of a day. This fluctuation may lead to the symptoms being more or less severe over time, and this has led some investigators to suggest the need for a specifier of subsyndromal delirium.[13•] Yet, there are currently no diagnostic criteria for subsyndromal delirium. Investigators have therefore based operational definitions on a smaller number of the core symptoms than required to meet the diagnostic threshold for delirium. In a recent study, Cole et al.[13•] looked at two possible definitions for subsyndromal delirium, one requiring one symptom on the confusion assessment method (CAM)[14] and the other requiring two symptoms (the CAM requires three symptoms for diagnosis of delirium). One hundred and four long-term care residents who were aged more than 65 years and did not have core symptoms for delirium were followed for 6 months. Sixty-eight developed one symptom over follow-up, whereas a much smaller group developed two symptoms. Those who developed two symptoms during the follow-up period had worse overall cognitive outcomes than those who experienced only one. Therefore, the development of subsyndromal delirium by this definition did predict a poorer outcome.

In another study, Meagher et al.[15•] performed twice weekly evaluations of 100 adults with DSM-IV delirium. Using generalized estimating equations, these investigators found that full syndromal delirium was significantly more severe than subsyndromal delirium for symptoms including delusions, hallucinations, agitation, retardation, orientation, attention, short-termand long-termmemory items, and cognitive test for delirium (CTD) symptoms including attention, vigilance, orientation, and memory.

From these two studies, it appears that, in investigations of individuals experiencing delirium symptoms, a syndrome can be identified as subsyndromal delirium if it falls between normality and full syndromal delirium.[16] Yet, what remains to be determined is whether such a distinction is clinically practical given the fluctuating course of delirium, as clinical manifestations may range from normality through subsyndromal to full syndromal delirium in a matter of hours.


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