Performance of the modified Richmond Agitation Sedation Scale in identifying delirium in older ED patients

Background Delirium in older emergency department (ED) patients is associated with severe negative patient outcomes and its detection is challenging for ED clinicians. ED clinicians need easy tools for delirium detection. We aimed to test the performance criteria of the modified Richmond Agitation Sedation Scale (mRASS) in identifying delirium in older ED patients. Methods The mRASS was applied to a sample of consecutive ED patients aged 65 or older by specially trained nurses during an 11-day period in November 2015. Reference standard delirium diagnosis was based on Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) criteria, and was established by geriatricians. Performance criteria were computed. Analyses were repeated in the subsamples of patients with and without dementia. Results Of 285 patients, 20 (7.0%) had delirium and 41 (14.4%) had dementia. The sensitivity of an mRASS other than 0 to detect delirium was 0.70 (95% confidence interval, CI, 0.48; 0.85), specificity 0.93 (95% CI 0.90; 0.96), positive likelihood ratio 10.31 (95% CI 6.06; 17.51), negative likelihood ratio 0.32 (95% CI 0.16; 0.63). In the sub-sample of patients with dementia, sensitivity was 0.55 (95% CI 0.28; 0.79), specificity 0.83 (95% CI 0.66; 0.93), positive likelihood ratio 3.27 (95% CI 1.25; 8.59), negative likelihood ratio 0.55 (95% CI 0.28; 1.06). Conclusion The sensitivity of the mRASS to detect delirium in older ED patients was low, especially in patients with dementia. Therefore its usefulness as a stand-alone screening tool is limited.