A shortened version of the Confusion Assessment Method took 3 minutes to administer and identified 95% of patients with delirium, compared with a reference standard that involved 1.5 hours of interviews and medical record reviews by a panel of experts, researchers reported online Oct. 20 in the Annals of Internal Medicine.
The 3-minute CAM (3D-CAM) also had a high estimated specificity (94%; 95% confidence interval, 90%-97%), although specificity was substantially lower (86%) in patients with dementia (95% CI, 67%-96%), probably because it can be difficult to distinguish delirium from dementia, said Dr. Edward Marcantonio of the Beth Israel Deaconess Medical Center in Boston and his associates. “Further research will focus on developing the optimal strategies for translating the 3D-CAM into routine care and determining whether improved detection of delirium can result in improved outcomes for vulnerable hospitalized older persons,” said the researchers (Ann. Intern. Med. 2014 Oct. 20 [doi:10.7326/M14-0865]).
The original CAM has been widely used since the 1990s and is regarded as accurate, but challenging to administer. To create the 3-minute version of the CAM, the investigators used a data set of 4,598 structured delirium assessments from a prior multisite trial in which they had selected the 36 items that best captured the four diagnostic features of the CAM. Those features include acute change or fluctuating course, inattention, disorganized thinking, and altered level of consciousness, said the investigators. They further reduced the 36-item list to 20 by using logistic regression to identify the most useful items for each diagnostic feature, they said.
The researchers then tested the 3D-CAM in a prospective cohort of 201 medical patients with a median age of 84 years. In all, 88% of patients were white, and 21% had been diagnosed with dementia, the researchers reported. An expert panel determined that 42 (21%) of these patients had delirium, of which 88% had hypoactive or normal psychomotor features, said Dr. Marcantonio and his associates.
When compared with this reference standard, the overall sensitivity of the 3D-CAM was 95% (95% CI, 84%-99%), and the test was similarly sensitive in patients with and without dementia, the researchers reported. Among nine false positives, six patients had subsyndromal delirium as determined by the expert panel, the investigators added.
The 3D-CAM took a median of 3 minutes to administer (interquartile range, 2-5 minutes), said the researchers. Because some 95% confidence intervals were wide and the study was conducted at one urban teaching hospital on a single day, they recommended validating the results in settings such as surgical wards and postacute and palliative care facilities.
The National Institute on Aging funded the study. The investigators declared no financial conflicts.