Delirium, characterized by acute changes in cognitive status, particularly attention and executive function , is common in older ED patients and makes them prone to adverse outcomes such as impaired functional status , prolonged hospital stay , cognitive decline , and increased mortality . Delirium prevalence in older ED patients has been estimated to be between 7% and 10% [6, 7].
However, the sensitivity of delirium detection in the ED appears to be poor [8–11]. Possible reasons for low detection rates occur on different levels. Patient-related risk factors such as hypoactive delirium have been identified . Further, mental status screening tools are complex, they are rarely used, and staff is inadequately trained in applying them [13, 14]. Environmental factors such as ED crowding, rapid workflow, and high decision density may also contribute. It therefore seems that the time needed to conduct an assessment is first and foremost pivotal for its application .
Although several tools for the detection of delirium have been developed, few have been studied in the ED. To our knowledge to date no study has evaluated the utility of formal delirium assessment in the ED setting, using a standardized instrument, compared to informal, clinical delirium detection.
The Confusion Assessment Method (CAM) is a widely used and validated tool for diagnosing delirium . When used by untrained clinicians, however, the sensitivity of the CAM is low . The CAM was validated using the Mini Mental State Examination (MMSE)  as a structured patient interview, which is an integral part of the assessment. However, the MMSE is too time-consuming for routine use in the ED, particularly because manual tasks such as writing and drawing are required.
The CAM-ICU is an adaptation of the CAM for use in the intensive care unit . It has also been used for research purposes in the ED . Although the CAM-ICU algorithm can be rapidly performed, the scale was developed for non-verbal responses  and may therefore, in addition to its low sensitivity , be not ideal for routine use in the ED setting.
Since established delirium screening tools appear to be too complex and too time consuming for the ED setting, or do not provide sufficient information about cognition, there is a need for a quick and sensitive ED screening method. To this end we developed an algorithm for delirium screening, detection and management in older ED patients. An integral part of the algorithm is the modified Confusion Assessment Method for the Emergency Department (mCAM-ED), a feasible approach based on the original short version of the CAM. Recently, Han and colleagues  proposed an approach for diagnosing delirium in the ED which is also an adaptation of the CAM. As in our study, the emphasis was on brevity to enhance feasibility. However, delirium assessment was performed by research personnel, and therefore the instrument’s feasibility for ED nurses at the bedside in a busy ED was not shown.
The aims of this study were threefold. First, to investigate whether there is a need for a standardized delirium screening and assessment instrument in the ED. Second, as we hypothesized that such an algorithm would improve delirium detection, we aimed to evaluate the feasibility of our new algorithm for delirium screening, detection and management, which includes the newly developed mCAM-ED as a screening and assessment instrument at the ED bedside. Third, we aimed to assess interrater reliability of the newly developed mCAM-ED.