Brief Report
Optimizing the month of the year backwards test for delirium screening of older patients in the emergency department

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Abstract

Introduction

Different scoring methods exist for the Month of the Year Backward Test (MBT), which is designed to detect inattention, the core feature of delirium. When used as a part of the modified Confusion Assessment Method for the Emergency Department (mCAM-ED), each error in the MBT scores one point. Because this scoring procedure is complex, we aimed to simplify the scoring method of the MBT.

Methods

This is a secondary analysis of a single center prospective validation study of the mCAM-ED comprising a sample of Emergency Department (ED) patients aged 65 or older presenting to our ED.

Data collection

Research assistants (RAs) who were trained nurses conducted the MBT. Geriatricians conducted the reference standard delirium assessment within 1 h of the RA.

Results

For the scoring method “number of errors”, optimal performance according the Youden index was achieved when 8 or more errors were reached resulting in an overall sensitivity of 0.95 and overall specificity of 0.94. The scoring method “number of errors in combination with time needed” resulted in a comparable result with minimally lower positive likelihood ratios. For the scoring method “last month in correct order”, optimal performance according the Youden index was achieved with the month of September resulting in an overall sensitivity of 0.90 and an overall specificity of 0.89.

Discussion

We suggest omitting the factor time and using a more practical scoring method with good performance: “last month in correct order” with the requirement to reach September to rule out delirium.

Introduction

Delirium in the Emergency Department (ED) is associated with increased hospital length of stay and 6-month-mortality [1,2]. As the main feature of delirium is inattention, measuring inattention with the Month of the Year Backwards Test (MBT) is a fast method to rule out delirium [3]. The MBT was previously suggested to be the best single delirium screening item, particularly due to its relative brevity and simplicity compared to other approaches [4,5]. However, difficulties in completing the MBT may also indicate the presence of significant cognitive problems such as dementia [3,6].

We previously developed and validated the modified Confusion Assessment Method for the Emergency Department (mCAM-ED), a two-step tool for delirium diagnosis in the emergency department (ED) [7,8]. In the first step, the Month of the Year Backwards Test (MBT) is used to rule out delirium. Different scoring methods exist for the MBT such as reciting the month backwards errorlessly to July or January [3,9]. In our study, in which the MBT was one component of the mCAM-ED, we used the scoring methods of counting the amount of errors according to Stillman et al. [9]: Each error in the MBT, defined as every pair of months that is not recited in the correct order, scores one point, and if the patient needs longer than 30 s for this task, an additional point is added. Because this scoring procedure is complex, we aimed to simplify the scoring method of the MBT and to determine the best cut-off score for delirium screening in the ED.

Section snippets

Setting

This is a secondary analysis of a single center prospective validation study of the mCAM-ED [8] comprising a sample of ED patients aged 65 or older presenting to our ED. The 24/7 consecutive data collection covered an 11-day period in November 2015. Patients were excluded if they were treated in the resuscitation bay, were unable to communicate verbally (e.g. aphasia, coma) or had other communication problems (e.g. severe hearing impairment, language barrier).

Month of the year backwards test (MBT)

Patients were asked to recite the

Results

For this subanalysis 286 patients with a median age of 80.02 (Q1 = 72.15; Q3 = 86.76), and of which 168 (58.7%) were female, were included. Dementia was documented in 41 (14.3%) out of 286 patients in the electronic medical record. According to the reference standard, 20 patients (7.0%) had delirium. Of those, 11 had delirium superimposed on dementia. Reciting the months backwards without any error was possible for 168 out of 236 (71.2%) patients without cognitive impairment, 8 out of 30

Main discussion

In comparison with the current scoring method “number of errors in combination with time needed”, in the scoring method “number of errors” an optimal performance of the MBT to indicate delirium in ED patients was achieved with a cut-off of 8 errors or more. Although slightly lower in performance, the scoring method “last month in correct order” using the September cutoff is easier. Using time as a factor did not provide additional value in the “number of errors in combination with time needed”.

Financial support

Scientific funds of the University Hospital Basel.

Declaration of Competing Interest

None.

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