OBJECTIVES: : The Family Confusion Assessment Method (FAM-CAM) has been validated in outpatient populations but has not been tested in populations with dementia or in hospitalized patients. This study compared delirium detection rates using the Family Confusion Assessment Methods (FAM-CAM) in caregivers of dementia patients versus those of non-dementia patients against a gold standard interviewer rating, Confusion Assessment Methods (CAM). METHODS: This observational study enrolled 108 elderly patient/family member dyads who presented to Emergency Department at the University campus of UMass Memorial Health Care. Upon admission, the research staffs used the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) to assess dementia in the patients. Two interviews were conducted to assess delirium in the patients as follows: each patient was interviewed by a trained rater using the CAM, and each family caregiver was guided through the FAM-CAM questionnaires. RESULTS: The average age of enrolled patients was 81 years old. IQCODE identified 51% of patients as having dementia. The prevalence of delirium was 28% according to both the CAM and the FAM-CAM. The sensitivity of the FAM-CAM was 60.8% (CI= 41-81%) in patients with dementia and 42.8% (CI=6-80%) in patients without dementia. The specificity of the FAM-CAM was 74.3% (CI=59-88%) in patients with dementia and 90.1% (CI=82-99%) in patients without dementia. CONCLUSIONS: The sensitivity was 20% higher in dementia patients, which shows that FAM-CAM performs better than CAM at recognizing delirium in dementia patients and supports validation of its use in high-risk patient population with Delirium Superimposed on Dementia (DSD). The FAM-CAM offers critical knowledge of family caregivers on patient’s baseline cognitive and physical function, therefore has great potential to help health care clinicians identify delirium during their patient assessment. Future studies with a larger sample size of different races and with education of caregivers on delirium-associated symptoms are encouraged.