References
Test
Pre-drawn clock
Time setting
Scoring criteria and range
Correlation with other measures
Goodglass et al. [30]
Drawing
Yes
1:00, 3:00, 9:15, 7:00
Subject asked to denote four different times. For each clock, 2 points awarded for correct placement of each hand (1 point each), and a third point is given for correct relative lengths of the hour and minute hands. A maximum of 3 points per clock, for a total of 12 points across all four clocks. Lower scores indicate higher impairment
Not assessed
Drawing
Yes
11:10
5 points awarded for “perfect” clock, 4 points for clock containing minor visuospatial errors, 3 points for acceptable visuospatial organization but inaccurate representation of 10 past 11, 2 points for moderate visuospatial disorganization of numbers, 1 point for a severe level of visuospatial disorganization, and 0 points for inability to make any reasonable attempt
MMSE = −0.65, SPMSQ = −0.66, GDS = −0.32
Morris et al. [32]
Drawing
No
8:20
4-point scoring system that uses the CERAD scale (0 = normal clock, 1 = mild impairment, 2 = moderate impairment, 3 = severe impairment). Assignment of scores is based on published clocks illustrating each level of impairment. A cutoff of greater than 0 (mild impairment or greater) used for classifying a clock as abnormal
MMSE (r = −.79, p < 0.001), CASI (r = −.80, p < 0.001)
Sunderland et al. [33]
Drawing
No
2:45
10-point scoring system with 1 as the lowest score and 10 as the highest score. Five points given for accurate drawing of a clock face with numbers placed correctly; remaining 6–10 points awarded for accuracy of hands denoting the time 2:45. Cut-off score of 6/10 indicates normal cognitive functioning
GDS (r = 0.56), DRS (r = 0.59), BDRS (r = 0.51), SPMSQ (r = 0.59, p < 0.001)
Wolf-Klein et al. [34]
Drawing
Yes
No
10-point system with scores corresponding to 10 hierarchical clock patterns from a previous pilot study. Cutoff score of less than 7 indicating “abnormal”
Not assessed
Mendez et al. [16]
Drawing
No
11:10
20-item scale with each clock attribute independently scored as a dichotomous variable. Attributes based on analysis of frequency of errors in clock drawing test
Rey complex figure = 0.66, symbol digit = 0.65, MMSE = 0.45, GDS = 0.40
Rouleau et al. [8]
Drawing and copying
No
11:10
10-point scale that independently assesses three subscales: (1) representation of clock face (maximum of 2 points); (2) layout of numbers (maximum of 4 points); position of hands (maximum of 4 points). Lower scores indicate greater impairment
Not assessed
Tuokko et al. [35]
Drawing, clock setting, clock reading
Yes
11:10
Errors on clock drawing categorized into the following classes: perseverations, omissions, rotations, misplacements, distortions, substitutions, and additions. Greater than two errors on clock drawing considered abnormal. Clock setting and clock reading achieve a maximum of 3 points. Greater than two errors is considered a positive (abnormal) result for clock drawing while the cut-off for the clock setting and clock reading tasks was a score of less than 13
Not assessed
Death et al. [36]
Drawing
Yes
No
Clocks were classified according to 4 classes: (1) Bizarre – major spacing abnormality; (2) Major spacing abnormality; (3) Minor spacing abnormality or single missing or extra number; (4) Completely normal. Cognitive impairment indicated by classes 1 and 2, while classes 3 and 4 indicate no cognitive impairment
Ability of normal clock (class 3 or 4) to predict a normal MMSE score of 24 or above was 90 %.
Ability of abnormal clock (class 1 or 2) to predict an abnormal MMSE score of 23 or below was 71 %.
Watson et al. [37]
Drawing
Yes
No
Clock is divided into four quadrants with the greatest weight assigned to the fourth quadrant (numbers 9–12). Each error falling into quadrants one, two and three contributes a score of 1, and each error in the fourth quadrant contributes a score of 4. Score of 0–3 indicates normality, while a score of 4 or greater indicates abnormality
Not assessed
Manos and Wu [38]
Drawing
Yes
11:10
10-point system with a transparent circle divided into eighths that acts as a scoring tool for the drawn clock. Points are awarded based on the numbers falling into their proper section and accuracy of hands. Cutoff score of 7/10 used by authors to indicate a “normal” clock
Trail making test part A (r = −0.48, p < 0.001), MMSE (r = 0.50, p <0.001), block design Test (r = 0.56, p < 0.001)
Royall et al. [17]
Drawing and copying
No
1:45
Maximum score on the drawing task (CLOX 1) is 15 points. Maximum score on the copying task (CLOX 2) is 15 points. Lower scores indicate impairment. Cutoff scores of 10/15 (drawing task) and 12/15 (copying task) to indicate normal functioning. Points are awarded based on the answers to a set of 15 questions (e.g., does figure resemble a clock? Outer circle present?)
EXIT25 (r = −0.78, p < 0.001), MMSE (r = 0.76, p < 0.001)
Lin et al. [39]
Drawing and copying
Yes
10:10
Maximum score of 16 for both the drawing and copying tasks, with higher scores indicating better performance. Clock face is divided into quadrants, and the placement of three numbers in a quadrant was considered correct. Points assigned based on the answers to 16 questions (yes = 1 point, no = 0 points) (e.g., does the drawing resemble a clock?)
Drawing and copying tasks significantly correlated with scores on the CASI (Pearson’s r = 0.73 and 0.67, p < 0.01), MMSE (Pearson’s r = 0.73 and 0.67, p < 0.01), and CDR (Spearman’s p = −0.47 and −0.37, p < 0.01)
Freund et al. [40]
Drawing
No
11:10
7-point scale with three subscales: (1) Time (3 points): two hands, one hand pointing to 2, absence of intrusive marks (e.g., tic marks, time written in text, incorrect time, etc.); (2) Numbers (2 points): numbers inside circle, all numbers present with no duplicates; (3) Spacing (2 points): equal spacing between numbers and between numbers and edge of circle
Not assessed
Babins et al. [41]
Drawing
No
11:10
18-point system where errors are grouped into five major categories: (1) Stimulus-bound errors (hands set for “10–11” or time is written beside the 11 or beside the 11 and 10); (2) Conceptual deficits (misrepresentation of clock itself); (3) Perseveration (number repetition or more than two hands); (4) Visuospatial organization (numbers outside circle or gaps in numbers); (5) planning deficits (additional or irrelevant marks and inappropriate spacing)
Pearson correlation between 18-point clock scoring system and MMSE (r = .476, p < .001)
Lessig et al. [42]
Drawing
No
8:20 or 11:10
Analyzed three existing scoring systems (Mendez et al. [16], Tuokko et al. [35], Shulman et al. [43]) to isolate six specific errors that were best able to discriminate patients with dementia from those without. A final algorithm was created from these six errors: inaccurate time setting, missing hands, missing numbers, number substitutions or repetitions, and failure to attempt clock drawing. If any error was identified, the clock was classified as abnormal
Not assessed
Parsey and Schmitter-Edgecombe [44]
Drawing
No
1:45
Modified scoring system based on qualitative error analysis of Rouleau et al. [8]. Sixteen-point scoring method, with a “perfect” clock indicated by the maximum 16 points. Each error deducts 1 point from this score. Errors grouped into the following six categories: perseveration, spatial or planning deficits, conceptual deficits, graphic difficulties, size of clock, and stimulus-bound responses
Shipley total score = .351, TICS total score = .663, SDMT oral total = .533, SDMT written total = .525, TMT part A = −.351/B = −.580, RAVLT trials 1–5 = .465, BNT total correct = .466, WAIS-III L-N Seq. = .533, Design fluency = .518, Letter fluency = .398, Category fluency = .527
Jouk and Tuokko [45]
Drawing
Yes
11:10
Further reduced the Lessig et al. [42] scoring system to include only five specific errors: repeated numbers, missing numbers, extra marks, number orientation, and number distance. If any error was identified, the clock was classified as abnormal
Not assessed
Nyborn et al. [46]
Drawing and copying
No
11:10
Drawings are assigned error scores (rather than correct scores) for 38 qualitative features. Includes overall summary error score, as well as subscale error scores related to outline, numeral placement, center, time-setting, and “other”. Numerals (0–9 points) and time-setting (0–7 points) subscales constitute majority of possible error points (total possible error points is 20.5)
Not assessed
Fig. 5.1
Severity scores from 5 to 0 (Reproduced from Shulman [2] with permission from John Wiley & Sons Ltd.)
Fig. 5.2
Errors in denoting 3 o’clock (Reproduced from Shulman [2] with permission from John Wiley & Sons Ltd.)
Fig. 5.3
Sensitivity to deterioration in dementia (Reproduced from Shulman [2] with permission from John Wiley & Sons Ltd.)
In perhaps its first systematic use, Goodglass et al. [30] included the CDT as part of the Boston aphasia battery. Their procedure involved clock setting where the subject was given four pre-drawn clock faces that include short lines marked in the positions of the 12 numbers. The subject was asked to denote four different times: 1:00, 3:00, 9:15, and 7:00. Points were awarded for each correct placement of a hand and 1 point each for correctly drawing the relative lengths of the minute and hour hands. A total of 3 points could be achieved for each clock for a maximum of 12 points on the test. The authors reported that age and education appeared to be influential factors only for subjects who scored in the bottom range on the test.
Shulman et al. [31] compared the CDT to the MMSE [47] and the Short Mental Status Questionnaire (SMSQ) [48] in a sample of 75 older adults with a mean age of 75.5 years. Three groups were included in their study, including those with dementia, those with depression, and normal controls. The authors developed a 5-point scale of severity of impairment, based on clinical experience. A score of 1 denoted very minimal error while a score of 5 was assigned when the subject was unable to make any reasonable attempt to draw a clock. In a subsequent study, this scoring was reversed and 5 points were awarded to a perfectly drawn clock [43]. Shulman’s current practice (see Fig. 5.1) is to assign 5 points for a “perfect” clock, 4 points for a clock with minor visuospatial errors, three for inaccurate representation of 10 past 11 when the visuospatial organization is done well, two for moderate visuospatial disorganization of numbers such that accurate denotation of “ten past eleven” is not possible, one for a severe level of visuospatial disorganization, and 0 for inability to make any reasonable representation of a clock [2].
Sunderland et al. [33] used a priori criteria to develop a 10-point scoring system with 10 as the highest score and 1 as the lowest score. Five points were awarded for drawing a clock face with numbers correctly placed, while 6–10 points were given for accuracy of drawing hands to denote the time 2:45. An arbitrary cut-off score of 6/10 was considered within normal limits. The authors reported that three out of 83 controls (3.6 %) scored less than 6, whereas 15 out of 67 patients with Alzheimer’s disease (22.4 %) scored more than 6. They also found high inter-rater reliability between clinicians and non-clinicians and high correlation of the CDT with other measures of dementia severity, including the Dementia Rating Scale. A later study by Kirby et al. [49] used this same scoring system while incorporating a more heterogeneous sample of community-dwelling participants. They found that the sensitivity of the CDT in the detection of dementia in the general community was 76 %. The specificities of the CDT against normal elderly and depressed elderly were 81 and 77 %, respectively.
Wolf-Klein et al. [34] compared their clock drawing test to the MMSE [47], Hachinski’s scale [50], and the Dementia Rating Scale [51] in a sample of outpatients being screened for cognitive impairment. Their methods included a pre-drawn circle and ten hierarchical clock patterns that were predetermined by a previous pilot study involving over 300 patients. Their patient groups included healthy normals, those with Alzheimer’s dementia and multi-infarct dementia, and others. A cut-off score of 7/10 reflected normal performance, and a score of less than seven was considered “abnormal.” With a focus on temporoparietal function, they found that scores of 1–6 were specific for Alzheimer’s disease as opposed to multi-infarct dementia or mixed cases.
A simple 4-point scoring system was developed by the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) [32]. In this method, subjects were instructed to draw a clock by first drawing a circle, then adding numbers and then setting the time to show 8:20. The instructions could be repeated, and if necessary, the subject could be instructed to draw a larger circle. In this system, a score of “0” implied an intact clock, 2 = mild impairment, 3 = moderate impairment, 4 = severe impairment. Thus, any score greater than 0 was considered abnormal for the purposes of classification [52]. The CERAD scoring method was later used by Borson et al. [52], who incorporated the CDT into the “Mini-Cog” battery, which also contains a simple three-word delayed recall memory test. The authors found the sensitivity and specificity for probable dementia were 82 and 92 %, respectively, for the CDT, compared to 92 and 92 % for the MMSE and 93 and 97 % for the Cognitive Abilities Screening Instrument (CASI) [53]. However, the authors noted that in poorly educated non-English speakers, the CDT detected demented subjects with higher sensitivity than the two longer instruments (sensitivity and specificity 85 and 94 % for the CDT, 46 and 100 % for the MMSE, and 75 and 95 % for the CASI). Furthermore, less information was lost due to non-completion of the CDT than the MMSE or CASI (severe dementia or refusal: CDT 8 %, MMSE 12 % and CASI 16 %).
Tuokko et al. [35] developed a unique procedure involving three empirically derived tasks that involved clock drawing, clock setting, and clock reading. The clock drawing component involved a pre-drawn circle in which the subject was asked to denote “ten past eleven.” Clock setting involved setting five different times, and clock reading involved the same clocks as in clock setting, but in a different order. Errors on clock drawing were classified into the following categories: omissions, perseverations, rotations, misplacements, distortions, substitutions, and additions. Clock setting achieved a maximum of 3 points, as did clock reading. Making more than two errors was considered a positive (abnormal) result for clock drawing, while the cut-off for the clock setting and reading tasks was a score of less than 13. Interestingly, errors from four categories (omissions, distortions, misplacements, and additions) were found to contribute significantly to the difference between normal elderly and Alzheimer’s disease patients.
Rouleau et al.’s [8] version of the CDT instructed subjects to “draw a clock, put in all the numbers, and set the hands for ten after eleven.” The participants were also asked to copy a pre-drawn clock. This version was designed to identify the quantitative and qualitative aspects of cognitive impairment in patients with Alzheimer’s disease. The test was scored is using a 10-point scale, with lower scores indicating greater cognitive impairment.
Death et al. [36] focused on elderly inpatients seen consecutively in surgical and medical wards at three hospitals in Newcastle, UK. Their CDT protocol involved giving the patient a piece of paper with a 10 cm heavy black circle with a dot in the center printed on it. They were asked to “imagine this is a clock face. Please fill in the numbers on the clock face.” If, while drawing, a patient spontaneously recognized an error and requested to correct it, he or she was allowed to do so. For scoring, clocks were classified as follows: bizarre (class 1), major spacing abnormality (class 2), minor spacing abnormality or single missing or extra number (class 3), and completely normal (class 4). Clocks class 1 and 2 indicated impairment, and class 3 and 4 indicated no cognitive impairment. The authors found that normal clock drawing ability reasonably excluded cognitive impairment or other causes of an abnormal MMSE in elderly acute medical and surgical hospital admissions where cognitive impairment is often missed.
The clock completion test developed by Watson et al. [37] involved providing patients with a pre-drawn circle and asking them to draw in the numbers on a clock face. Interestingly, in this method, the patients were not asked to draw the hands on the clock, and scoring included only the positioning of the clock numbers. The scoring system divided the pre-drawn circle into four quadrants, assigning greatest weight to the fourth quarter. An error made in quadrants one, two, or three received a score of 1, and any error in quadrant four (containing numbers 9–12) received a score of 4. A score of 0–3 was considered normal, and anything ≥4 was considered abnormal. In the original study, the authors studied a group of patients from a geriatric outpatient assessment clinic and found an excellent comparison with the Blessed Orientation-Memory-Concentration test [54].
Manos and Wu [38] developed a “10-point clock test” that included a scoring system utilizing a transparent circle divided into eighths that was applied to the clock drawn by the patient. A maximum of 10 points were awarded for numbers falling into their proper segment and for correctly drawn hands. A difficulty with this method is that some significant errors will not be scored, such as counterclockwise placement of numbers or numbers that are positioned outside the circle. The authors found that a cut-off score of 7 out of 10 identified 76 % of patients with dementia and 78 % of control patients. A later study using the same test attempted to identify mild AD patients (i.e., those with MMSE >23) among consecutive ambulatory patients. The author reported a sensitivity of 71 %, compared to 76 % for the original study that included patients with a mean MMSE score of 20 [55].
A “simple scoring system” (SSS) was developed by Shua Haim et al. [56]. The authors performed a retrospective chart analysis of a sample of elderly patients in an outpatient memory disorders clinic. Their scoring system was based largely on the visuospatial aspects of the task and the correct denotation of time by the hands for a maximum of 6 points. A formula was developed to relate clock scores with the MMSE using simple linear regression in the following way: MMSE = 2.4 × (the clock score) + 12.7. The authors reported that a clock score of zero predicts an MMSE score of <13, whereas a clock score of 6 predicts a MMSE score of ≥27.
Lin et al. [39] examined a comprehensive scoring system of the CDT in screening for Alzheimer’s disease in a Chinese population in order to derive a simplified scoring system. In this study, the clocks were first scored based on the systems described by Watson et al. [37], Wolf-Klein et al. [34], and Tuokko et al. [35], which involved first dividing the clocks into quadrants using two reference lines – one line through the center and the numeral 12, and then a second line perpendicular to the first one through the clock center. If a numeral was placed on the reference line, it was included in the quadrant clockwise to the line. Thirteen criteria were then scored as correct or incorrect for a maximum total score of 16 (item six received up to 4 points for correct placement of three numerals in each of the four quadrants). The authors then formulated a simple scoring system of only three items (hour hand, number 12, and difference between hands) using a stepwise discriminant analysis to select a minimal set of items from the comprehensive scoring system. The simplified 3-item scoring, with a cut-off score of 2/3, was found to have a sensitivity of 72.9 % and a specificity of 65.6 %. The authors suggest that this simple scoring method can be used as a quick test for AD screening.
Lessig et al. [42] analyzed the scoring systems of Shulman et al. [43], Mendez et al. [16] and Wolf-Klein et al. [34], as well as the CDT system used in the Mini-Cog [52] in order to identify an optimal subset of clock errors for dementia screening. The clock drawings of 364 ethnolinguistically and educationally diverse subjects with ≥5 years of education were analyzed. An algorithm using the six most commonly made errors of inaccurate time setting, no hands, missing numbers, number substitutions or repetitions, and failure to attempt clock drawing detected dementia with 88 % specificity and 71 % sensitivity. A stepwise logistic regression found the simplified scoring system to be more strongly predictive of dementia than the three other CDT scoring systems. Also, substituting the new CDT algorithm for that used in the original version of the Mini-Cog improved the test’s specificity from 89 to 93 % with minimal change in sensitivity.
Babins et al. [41] developed “the 18-point clock-drawing scoring system” based on clinical intuition as well as a literature review. The goal of their system was to enhance the utility of the CDT for recognition and prognostication in mild cognitive impairment (MCI). In this system, errors were grouped into the following major categories: stimulus-bound errors, conceptual deficits, perseverations, visuospatial organization, and planning deficits. Using this scoring system with a sample of 123 retrospectively assessed individuals from a memory clinic in Montreal, the authors found that there were three significant hand items that appeared to be possible early markers of progression to dementia. The items “clock has two hands,” “hour hand is towards correct number” and “size difference of hands is respected” all showed significant differences between progressors and non-progressors. The authors suggested that the 18-point clock drawing scoring system may have advantages in identifying MCI individuals who are more likely to progress to dementia.
In an interesting twist on the standard administration and scoring of the CDT, Royall and colleagues [17] developed a variant of the clock drawing test (CLOX) designed to detect executive impairment and differentiate it from nonexecutive visuospatial failure. This version of the test is divided into two parts to distinguish the executive control of clock drawing from the constructional/visuospatial ability. For the first part of the test (CLOX 1), the subject is asked to “draw me a clock that says 1:45. Set the hands and numbers on the face so that a child could read them.” The notion underlying the method for CLOX 1 is that it reflects performance in a novel and ambiguous situation eliciting the executive skills of goal setting, planning, motor sequencing, selective attention and self-monitoring of a subject’s current action plan. Some of the CLOX 1 instructions are deliberately designed to distract the subject. For example, use of the terms “hand” and “face” has the potential to elicit semantic intrusions because they are more commonly associated with body parts than with elements of a clock. The maximum score for CLOX 1 test is 15. The second portion of the task (CLOX 2) involves a simple copying task of a pre-drawn clock already set at 1:45. Differences in scores on CLOX 1 and 2 are hypothesized to reflect executive contribution to the clock drawing test versus visuospatial and constructional ability. The participant’s performance is rated on a 15-point scale (lower scores indicate impairment) on both CLOX 1 and 2. Cut points of 10/15 (CLOX 1) and 12/15 (CLOX 2) represent the fifth percentile for young adult controls. A later study by the same authors found the CLOX test explained more variance in executive control function than other clock drawing tests [57].
Very recently, Jørgensen et al. [58] attempted to develop a reliable, short, and practical version of the CDT for clinical use. A main goal of their study was to produce a scoring method with high interrater reliability, which is a psychometric characteristic of the CDR that has been found to decline with increased scoring system complexity. Using a pilot study, the authors initially produced a 9-item scoring system that was developed based on Lin et al.’s [39] 13-item system. Four clinical neuropsychologists who were blind to diagnostic classification then scored clock drawings from 231 participants. The interrater agreement of individual scoring criteria was analyzed and items with poor or moderate reliability were excluded. This produced a 6-item CDT, which was examined to determine its classification accuracy. The authors found that, at a cutoff value of 5/6, the 6-item CDT had a sensitivity of 0.65 and a specificity of 0.80. Furthermore, stepwise removal of up to three items reduced the sensitivity only slightly (i.e., from 0.65 to 0.59). Classification accuracy associated with a score of 4/6 or less was reportedly very high (sensitivity = 0.63, specificity = 0.80).
5.5 Comparing CDT Scoring Systems
Table 5.2 shows the psychometric properties of the CDT scoring systems as determined by some of the comparison studies discussed in this section. Scanlan et al. [62] examined 80 clock drawings by subjects with known dementia status from four categories (i.e., normal, mild, moderate, and severe abnormality) as defined by the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD). In order to compare dementia detection across scoring systems, an expert rater scored all clocks using published criteria for seven systems, including Shulman et al. [31], Morris et al. [32], Sunderland et al. [33], Wolf-Klein et al. [34], Mendez et al. [16], Manos and Wu [38], and Lam et al. [29]. Additionally, 20 naïve raters with no formal instruction judged each clock as either normal or abnormal. The authors found that when using categorical cut-off points published for each CDT scoring system, the overall concordance between the naïve scores and the different CDT systems was high (86–89 %), with the exception of the Sunderland (73 %) and Wolf-Klein (66 %) systems. When CDT classifications were compared against independent clinical dementia diagnoses, the Mendez system most accurately distinguished demented from non-demented individuals, followed closely by the CERAD system. Naïve raters did not differ from the Manos or Shulman systems but were significantly better than the Lam, Sunderland, and Wolf-Klein systems. The CERAD and Mendez systems were found to be most sensitive in detecting mild and moderate dementia, however the Wolf-Klein system failed to detect some subjects who were presenting with severe dementia. Of note is that the Wolf-Klein system requires no time setting and mild to moderate number spacing errors are disregarded, both factors that likely contributed to poor performance of this system. Interestingly, the authors reported that detection of both MCI and mildly demented subjects was minimally two to three times greater than physician recognition for all systems except the Sunderland and Wolf-Klein systems [62].
Table 5.2
Psychometric properties of the Clock Drawing Test
References | Setting | Diagnostic criteria | Scoring systems compared | Sensitivity % | Specificity % | Area under ROC curve (AUC) | Interrater reliability | Test-retest reliability |
|---|---|---|---|---|---|---|---|---|
Tuokko et al. [59] | Canadian Study of Health and Aging (CSHA) | Comprehensive clinical examination; classified using DSM-III-R, NINCDS-ADRDA, ICD | Shulman et al. [31] Tuokko et al. [35] Watson et a. [37] Wolf-Klein et al. [34] Doyon et al. [60] | 93 91 59 74 54 | 48 50 67 72 91 | 0.79 0.78 0.67 0.79 0.80 | 0.83a 0.99 0.98 0.81 0.91 | 0.90a 0.97 0.84 0.96 0.81 |
Storey et al. [61] | General geriatric outpatient clinic in southwest Sydney, Australia | Comprehensive cognitive and physical assessment; classified using DSM-IV criteria | Mendez et al. [16] Shulman et al. [31] Sunderland et al. [33] Watson et al. [37] Wolf-Klein et al. [34] CERAD; Borson et al. [52] | 98 90 86 82 78 90 | 16 28 35 30 58 28 | 0.70 0.66 0.72 0.60 0.66 0.64 | 0.93b 0.93 0.84 0.81 0.93 – | 0.94b 0.96 0.87 0.89 0.93 – |
Scanlan et al. [62]c | University of Washington’s Alzheimer’s Disease Research Center Satellite Registry | CERAD expanded history, Clinical Dementia Rating; confirmed with formal diagnostic criteria (CERAD, DSM-IV, NINCDS-ADRDA) | Shulman et al. [31] CERAD; Morris et al. [32] Sunderland et al. [33] Wolf-Klein et al. [34] Mendez et al. [16] Manos & Wu [38] Lam et al. [29] Naïve Raters | 79.1 95.3 60.5 41.5 90.7 81.4 74.4 83.7 | 80.0 64.0 88.0 88.0 76.0 80.0 80.0 76.0 | – | 0.59c 0.63 0.42 0.25 0.67 0.59 0.51 0.59 | – |
Van Der Burg et al. [63] | Belgium study on health care needs of patients with dementia | Cambridge Examination for Mental Disorders of the Elderly – Revised (CAM-DEX-RN) | Shulman [2] Roth et al. [64] | 96 97 | 42 32 | – | 0.35c 0.63 | – |
Nair et al. [65] | Archival data from Boston University Alzheimer’s Disease Core Center registry | Clinical interview with participant and informant, medical history review, neurological and neuropsychological examination results | Dichotomous Ratingd Ordinal Rating Cutoff ≥1 ≥2 ≥3 ≥4 | 75 98 84 66 54 | 81 46 76 90 94 | – | 0.85 0.92 | – |
Jouk et al. [45] | Canadian Study on Health and Aging (CSHA) | Clinical examination including neuropsychological assessment; DSM-III-R dementia criteria | Jouk et al. [45] Lessig et al. [42] Shulman et al. [43] Tuokko et al. [66] Watson et al. [37] Wolf-Klein et al. [34] | 81 84 93 91 59 74 | 68 54 48 46 67 72 | 0.75 0.69 0.70 0.70 0.63 0.73 | – |
Van der Burg et al. [63] compared the dementia screening performance of two scoring systems, the CERAD system [32, 52] and the Shulman et al. [43] system, to determine whether a somewhat more complex system has clear advantages over a simpler and less time-consuming scoring system. The authors selected the simple 4-item CERAD method because of its user-friendly qualities and the Shulman 6-item system because of its proven diagnostic qualities. A total of 473 drawings was selected from a larger sample of 1199 elderly subjects for whom the presence or absence of dementia was known. Results showed that both scoring systems had good inter-system and inter-rater reliabilities and both correlated equally well with the true diagnosis of dementia. These findings are similar to earlier studies by Scanlan et al. [62] and Lin et al. [39], which also concluded that simpler systems were found to be accurate when compared to more complex systems. The authors concluded that primary care physicians and other health-care providers should be encouraged to use the simpler 4-item scoring checklist as it is easier to administer and requires less time than the 6-item method [63].
Matsuoka et al. [67] identified brain regions associated with performance on various measures of the CDT using magnetic resonance imaging (MRI) in 36 patients with Alzheimer’s disease, eight with mild cognitive impairment and four healthy controls. Multiple regression analyses were used to identify relationships between each CDT scoring system (Shulman [2], Rouleau [8] and CLOX 1 [17]), and regional gray matter volume. The authors reported that the CDT scores of the three scoring systems were positively correlated with gray matter volume in various regions in the brain. Furthermore, some brain regions overlapped with the three different scoring systems, whereas other regions showed differences between tests. All three CDT scoring systems were positively correlated with gray matter volume in the right parietal lobe. Furthermore, the Shulman system was positively correlated with gray matter volume in the bilateral posterior temporal lobes, leading the authors to speculate that the Shulman CDT might be useful in detecting the impairment of semantic knowledge and comprehension. The Rouleau CDT score was positively correlated with gray matter volume in the right parietal lobe, right posterior inferior temporal lobe and right precuneus, suggesting that the Rouleau CDT may detect impairment of visuospatial ability and the retrieval of visual knowledge. Finally, the CLOX 1 score was positively correlated with gray matter volume in the right parietal lobe and right posterior superior temporal lobe, suggesting that the CLOX 1 system may detect impairment in visuospatial ability and sentence comprehension. The authors concluded that distinct brain regions might be associated with CDT performance using different scoring systems and that different scoring and administration systems require different cognitive functions. Thus, rather than using only one scoring system, a combination of CDT scoring systems may cover a wider range of brain functions in dementia screening [67].
Recently, Mainland et al. [68] conducted a literature review of studies published between 2000 and 2013 to synthesize the available evidence on CDT scoring systems’ effectiveness and to recommend which system is best suited for use at the clinical frontlines. The authors found that, despite significant variations that emphasize visuospatial and executive functions to varying degrees, the psychometric properties of most systems are remarkably similar. When used specifically as a dementia screening measure in clinical settings, this finding is important considering the increased time required for scoring more complex systems. The authors concluded that, based on their review of the literature, expert consensus appears to support the notion that “simpler is better” when selecting scoring systems for dementia screening because of their strong psychometric properties and ease of use. In fact, Scanlan et al. [62] reported that simple judgment of “normal” versus “abnormal” clock drawings by naïve raters provides screening accuracy comparable with published scoring systems when distinguishing demented from non-demented individuals. Further support for the use of simpler scoring methods for the purpose of cognitive screening was provided by Kørner et al. [69], who examined five different scoring systems in a sample of Danish participants and found that, as the predictive values of each scoring system were nearly identical, the shortest scoring system was preferred.
5.6 Predictive Validity of CDT
5.6.1 Normal Aging
Bozikas et al. [70] administered Freedman et al.’s [27] version of the CDT to 223 healthy community-dwelling adults in order to develop norms for the Greek population and to explore the influence of demographic factors (i.e., sex, age, and level of education) on the performance of healthy individuals. The authors found no sex differences in performance but did find that age and level of education contributed to CDT scores. More specifically, they found that greater years of education were associated with better performance, while age had a negative contribution. Analysis revealed that the influence of age was due exclusively to the elderly group; for those patients under the age of 60 years, age did not influence CDT performance. However, there was a marked decline after 60 and another decline after 70 years of age. The authors suggest that performance on the CDT is resistant to the aging process, at least in the non-elderly. However, the authors note that future research should establish more reliable norms for the elderly by including more extensive sampling of elderly patients with varying levels of education.
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