The CAM-S: development and validation of a new scoring system for delirium severity in 2 cohorts.

BACKGROUND Quantifying the severity of delirium is essential to advancing clinical care by improved understanding of delirium effect, prognosis, pathophysiology, and response to treatment. OBJECTIVE To develop and validate a new delirium severity measure (CAM-S) based on the Confusion Assessment Method. DESIGN Validation analysis in 2 independent cohorts. SETTING Three academic medical centers. PATIENTS The first cohort included 300 patients aged 70 years or older scheduled for major surgery. The second included 919 medical patients aged 70 years or older. MEASUREMENTS A 4-item short form and a 10-item long form were developed. Association of the maximum CAM-S score during hospitalization with hospital and posthospital outcomes related to delirium was evaluated. RESULTS Representative results included adjusted mean length of stay, which increased across levels of short-form severity from 6.5 days (95% CI, 6.2 to 6.9 days) to 12.7 days (CI, 11.2 to 14.3 days) (P for trend < 0.001) and across levels of long-form severity from 5.6 days (CI, 5.1 to 6.1 days) to 11.9 days (CI, 10.8 to 12.9 days) (P for trend < 0.001). Representative results for the composite outcome of adjusted relative risk of death or nursing home residence at 90 days increased progressively across levels of short-form severity from 1.0 (referent) to 2.5 (CI, 1.9 to 3.3) (P for trend < 0.001) and across levels of long-form severity from 1.0 (referent) to 2.5 (CI, 1.6 to 3.7) (P for trend < 0.001). LIMITATION Data on clinical outcomes were measured in an older data set limited to patients aged 70 years or older. CONCLUSION The CAM-S provides a new delirium severity measure with strong psychometric properties and strong associations with important clinical outcomes. PRIMARY FUNDING SOURCE National Institute on Aging.