The CDT is used to quickly assess visuospatial and praxis abilities, and may determine the presence of both attention and executive dysfunctions (Adunsky, Fleissig, Levenkrohn, Arad, & Nov, 2002; Suhr, Grace, Allen, Nadler, & McKenna, 1998; McDowell & Newell, 1996).
The CDT is a simple task completion test in its most basic form. There are several variations to the CDT:
Free drawn clock: the individual is given a blank sheet of paper and asked first to draw the face of a clock, place the numbers on the clock, and then draw the hands to indicate a given time. To successfully complete this task, the patient must first draw the contour of the clock, then place the numbers 1 through 12 inside, and finally indicate the correct time by drawing in the hands of the
Pre-drawn clock: alternatively, some clinicians prefer to provide the individual with a pre-drawn circle and the patient is only required to place the numbers and the hands on the face of the clock. They argue that the patient’s ability to fill in the numbers may be adversely affected if the contour is poorly drawn. In this task, if an individual draws a completely normal clock, it is a fast indication that a number of functions are intact. However, a markedly abnormal clock is an important indication that the individual may have a cognitive deficit, warranting further investigation.
Regardless of which type is used (free drawn or pre-drawn), the verbal command CDT can simultaneously assess a patient’s language function (verbal comprehension); memory function (recall of a visual engram, short-term storage, and recall of time setting instructions); and executive function. The verbal command variation of the CDT is highly sensitive for temporal lobe dysfunction (due to its heavy involvement in both memory and language processes) and frontal lobe dysfunction (due to its mediation of executive planning) (Shah, 2002).
the individual is given a fully drawn clock with a certain time pre-marked and is asked to replicate the drawing as closely as possible. The successful completion of the copy command requires less use of language and memory functions but requires greater reliance on visuospatial and perceptual processes.
Clock reading test: a modified version of the copy command CDT simply asks the patient to read aloud the indicated time on a clock drawn by the examiner.
The copy command clock-drawing and clock reading tests are good for
assessing parietal lobe lesions such as those that may result in hemineglect. It is important to do both the verbal command and the copy command tests for every patient as a patient with a temporal lobe lesion may copy a pre-drawn clock adequately, whereas their clock drawn to verbal command may show poor number spacing and incorrect time setting. Conversely, a patient with a parietal lobe lesion may draw an adequate clock to verbal command, while their clock drawing with the copy command may show obvious signs of neglect.
The most common setting chosen by clinicians is “3 O’clock” (Freedman, Leach, Kaplan, Winocur, Shulman, & Delis, 1994). Although this setting adequately assesses comprehension and motor execution, it does not indicate the presence of any left neglect the patient may have because it does not require the left half of the clock to be used at all. The time setting “10 after 11” is an ideal setting (Kaplan, 1988). It forces the patient to attend to the whole clock and requires the recoding of the command “10” to the number “2” on the clock. It also has the added advantage of uncovering any stimulus-bound errors that the patient may make. For example, the presence of the number “10” on the clock may trap some patients and prevent the recoding of the command “10” into the number “2.” Instead of drawing the minute hand towards the number “2” on the clock to indicate “10 after,” patients prone to stimulus-bound errors will fixate and draw the minute hand toward the number “10” on the clock.
There are a number of different ways to score the CDT. In general, the scores are used to evaluate any errors or distortions such as neglecting to include numbers, putting numbers in the wrong place, or having incorrect spacing (McDowell & Newell, 1996). Scoring systems may be simple or complex, quantitative or qualitative in nature. As a quick preliminary screening tool to simply detect the presence or absence of cognitive impairment, you may wish to use a simple quantitative method (Lorentz et al., 2002). However, if a more complex assessment is required, a qualitative scoring system would be more telling.
Different scoring methods have been found to be better suited for different subject groups (Richardson & Glass, 2002; Heinrik, Solomesh, & Berkman, 2004). In patients with stroke, no single standardized method of scoring exists. Suhr, Grace, Allen, Nadler, and McKenna (1998) examined the utility of the CDT in localizing lesions in 76 patients with stroke and 71 controls. Six scoring systems were used to assess clock drawings (Freedman et al., 1994; Ishiai, Sugishita, Ichikawa, Gono, & Watabiki, 1993; Mendez, Ala, & Underwood, 1992; Rouleau, Salmon, Butters, Kennedy, & McGuire, 1992; Sunderland et al., 1989; Tuokko, Hadjistavropoulos, Miller, & Beattie, 1992; Watson, Arfken, & Birge, 1993; Wolf-Klein et al., 1989). Significant differences were found between controls and patients with stroke on all scoring systems for both quantitative and qualitative features of the CDT. However, quantitative indices were not helpful in differentiating between various stroke groups (left versus right versus bilateral stroke; cortical versus subcortical stroke; anterior versus posterior stroke). Qualitative features were helpful in lateralizing lesion site and differentiating subcortical from cortical groups.
A psychometric study in patients with stroke by South, Greve, Bianchini, and Adams (2001) compared three scoring systems: the Rouleau rating scale (1992); the Freedman scoring system (1994), and the Libon revised system (1993). These scoring systems were found to be reliable in patients with stroke (please see for the details of this study).
None typically reported.
Only a paper and pencil is required. Depending on the method chosen, you may need to prepare a circle (about 10 cm in diameter) on the paper for the patient.
The CDT can be administered by individuals with little or no training in cognitive assessment. Scanlan, Brush, Quijano, & Borson (2002) found that a simple binary rating of clock drawings (normal or abnormal) by untrained raters was surprisingly effective in classifying subjects as having dementia or not. In this study, a common mistake of untrained scorers was failure to recognize incorrect spacing of numbers on the clock face as abnormal. By directing at this type of error, concordance between untrained and expert raters should improve.
All variations of the CDT should take approximately 1-2 minutes to complete
(Ruchinskas & Curyto, 2003).
The Clock Drawing Test-Modified and Integrated Approach (CDT-MIA) is a 4-step, 20-item instrument, with a maximum score of 33. The CDT-MIA emphasizes differential scoring of contour, numbers, hands, and center. It integrates 3 existing CDT’s:
Freedman et al’s free-drawn clock (1994) on some item definitions
Scoring techniques adapted from Paganini-Hill, Clark, Henderson, & Birge (2001)
Some items borrowed from Royall, Cordes, & Polk (1998) executive CLOX
The CDT-MIA was found to be reliable and valid in individuals with dementia, however this measure has not been validated in the stroke population (Heinik et al., 2004).
Can be used as a screening instrument with:
Virtually any patient population (Wagner, Nayak, & Fink, 1995). The test appears
to be differentially sensitive to some types of disease processes. Particularly, it has proven to be clinically useful in differentiating among normal elderly, patients with neurodegenerative or vascular diseases, and those with psychiatric disorders, such as depression and schizophrenia (Dastoor, Schwartz, & Kurzman, 1991; Heinik, Vainer-Benaiah, Lahav, & Drummer, 1997; Lee & Lawlor, 1995;
Shulman, Gold, & Cohen, 1993; Spreen & Strauss, 1991; Tracy, De Leon, Doonan, Musciente, Ballas, & Josiassen, 1996; Wagner et al., 1995; Wolf-Klein, Silverstone, Levy, & Brod, 1989).
Can be used with: patients with stroke. Because the CDT requires a nonverbal response, it may be administered to those with speech difficulties but who have sufficient comprehension to understand the requirement of the task.
Should not be used in:
Patients who cannot understand spoken or written instructions
Patients who cannot write
As with many other neuropsychological screening measures, the CDT is affected by age, education, conditions such as visual neglect and hemiparesis, and other factors such as the presence of depression (Ruchinskas & Curyto, 2003; Lorentz, Scanlan, & Borson, 2002). The degree to which these factors affect ones score depends much on the scoring method applied (McDowell & Newell, 1996). Moreover, the CDT focuses on right hemisphere function, so it is important to use this test in conjunction with other neuropsychological tests (McDowell & Newell, 1996).
The CDT can be conducted in any language. Borson et al. (1999) found that language spoken did not have any direct effect on CDT test performance.