SUPPLEMENTARY MATERIALS
Detailed description of the Edinburgh Delirium Test Box (EDTB) Mark 2 device and
EDTB-ICU tests.
The EDTB instrument
The EDTB consists of a grey plastic box (13 x 21.5 x 7.5 cm), with two protruding
illuminable buttons (5 cm diameter) which can be pressed to respond to a task, or used
as lights for counting. In the present EDTB-ICU paradigm, the illuminable buttons
were only used to present lights; patients were not required to provide button presses.
The box also contains a concealed central 7 x 7 matrix of LEDs to display distracting
stimuli such as checkered patterns (which were not used in the present EDTB-ICU
paradigm) and four LEDs surrounding each illuminable button. All lights illuminate
as a red colour in order to provide distinctive stimuli which would be clearly visible
against the grey test box.
The test box is attached by a lead to a hand-held processing unit, from which the
assessor can select from a number of tasks stored to the internal memory of this
device, which were programmed by the researchers specifically for this study.
During the EDTB-ICU assessment the EDTB is presented to participants in portrait
orientation, with the single large target light on top (Supplementary Figure 1). The
four LED lights surrounding the target light were used as distracting stimuli.
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The EDTB-ICU assessment
The EDTB-ICU assessment consists of a behavioral assessment, followed by nine
attentional tasks (Figure 1).
EDTB-ICU behavioral assessment
The behavioral assessment consists of three parts:
1. The ability of each patient to open their eyes to verbal stimuli is assessed. If the
patient does not respond to their name with eye opening they are deemed nonassessable; if they respond the assessment continued.
2. Next, patients are asked to track moving visual stimuli (the investigator’s finger,
a pen, or identification badge) as it is moved slowly back and forth in front of
their eyes at a distance of approximately 30cm. If the patient is able to track the
stimulus for approximately 5 sec the assessment continues. If not, the instructions
and procedure are repeated, and if they are still unable to track the stimuli, they
receive a score of 0 and the assessment ceases.
3. The final part assesses both the patient’s ability to understand instructions that
will enable their participation in the attentional tasks, as well as establishing a
method of response for patients that are not able to respond verbally. If a patient
is able to respond to one of the tasks outlined below, the assessor continues to the
EDTB attention tasks. If the patient is unable to respond to the task within 10
seconds, the instructions and procedure are repeated once, and if the patient still
can’t respond the assessor will proceed to the next response method. If the patient
is unable to complete any of the following methods, they are given a score of 1
and testing is ceased.
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It is not mandatory to assess all response methods. Assessors may skip any methods
of response that are inappropriate (e.g. the patient will not be asked to respond
verbally if they are intubated); and if an appropriate method has already been
established (e.g. if the patient has already demonstrated the ability to communicate
verbally, or by nodding, etc.) then the assessor will skip directly to this method,
simply assessing their ability to follow an instruction.
For participants who have already demonstrated an ability to respond verbally, the
researcher holds the response card in front of the patient, points to any number printed
on the card, and asks the participant ‘what number is this?'.
Participants who are non-verbal are first asked to point to a given number on the
response card, held in front of them (within arm’s reach) by the assessor. Participants
who are able to indicate a response by pointing (regardless of accuracy) progress to
the EDTB-ICU assessment.
Researchers then sequentially ask patients whether they are able to squeeze the
researcher’s hand; to give a ‘thumbs-up’; to nod their head; or stick out their tongue.
After each instruction, if the participant still does not respond or is unable to perform
the gesture, the instruction for the next method is given.
EDTB-ICU attention task
The EDTB-ICU attentional tasks consist of nine trials, divided into three levels of
increasing difficulty mediated by presence and frequency of distracting stimuli, and
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increasing latency between target illuminations (Table 3). In all trials the target light
illuminate between 3-6 times, with a duration of 750ms per illumination.
Three sets of the EDTB-ICU task (each comprising nine trials) were constructed to
administer to patients undergoing longitudinal assessments, to minimize practice
effects. Only the number of target illuminations (though all between 3-6 illuminations
per trial) differs between these sets (Supplemental Table 1). There were no differences
in total scores between the three different sets of the EDTB-ICU (X2 (2) = 1.018, p =
0.60), suggesting that these were comparable in terms of task difficulty.
Supplemental Table 1. Description of the structure of the EDTB-ICU attentional
assessment.
Task
Trial
No. target
No. target
No. target
Inter-
No.
Frequency
illuminations
illuminations
illuminations
stimulus
distractor
of
(Set 1)
(Set 2)
(Set 3)
latency
lights
distractors
4
4
4
2000 ms
3
700 ms
Trial 1
3
4
5
1000 ms
None
N/A
Trial 2
5
5
6
2000 ms
None
N/A
Trial 3
4
3
4
3000 ms
None
N/A
Trial 4
5
5
3
1000 ms
3
700 ms
Trial 5
4
6
5
2000 ms
3
700 ms
Trial 6
4
4
4
3000 ms
3
700 ms
Trial 7
6
5
5
1000 ms
6
200 ms
Trial 8
5
3
4
2000 ms
6
200 ms
Trial 9
3
4
3
3000 ms
6
200 ms
level
Practice
Trial
1
2
3
4
Following each trial, the participant is presented with the response card, and asked to
select the answer using the response method established during the behavioral
assessment. If no response is given instructions are repeated, and if still no response is
given, the participant is given a score of 0 for that trial, and testing continues with the
next trial.
Response Cards
These response cards were developed specifically for use in patients unable to speak,
consisting of a laminated A4 page evenly divided into quarters with each section
containing a number (3, 4, 5, or 6) in size 150 Arial font.
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SUPPLEMENTARY FIGURES
(a)
(b)
Supplementary Figure 1: The Edinburgh Delirium Test Box (EDTB) Mark with (a)
the target light (which the participant is asked to count) and (b) three distracter lights
shown (which the participant is asked to ignore).
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Supplementary Figure 2: Receiver Operating Characteristic (ROC) curves for EDTB-ICU
assessment scores and CAM-ICU delirium diagnosis on patients’ first assessment (A); and
across all assessments (B).
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