Screening for Alzheimer's Disease by Clock Drawing

Abstract

The fear of Alzheimer's disease for both patients and families is growing along with the increasing evidence of the disease itself. This study (N = 312) of the validity of the clock drawing test in screening patients with probable Alzheimer's disease was conducted in an active outpatient geriatric clinic. Clock drawings by patients with normal mental status or depression were essentially normal. Alzheimer's patients were unable to complete a normal clock and demonstrated five characteristically abnormal patterns. As a test for Alzheimer's disease, clock drawing had a sensitivity of 86.7% and a specificity of 92.7%. There was correct identification in 97.2% of normals. These findings indicate that the clock drawing test, an easily administered, low cost screening tool, can be useful to health care professionals in characterizing cognitive loss in a general geriatric clinic population.

The Clock Drawing Test: performance among elderly with low educational level

“…A clock drawing task is part of this instrument and uses the following instruction: "Draw the face of a large clock, place all the numbers inside and place the pointers indicating 11:10 (eleven hours and ten minutes)". The clock drawing of each patient -copied and identified with its respective register number -was analyzed retrospectively by five researchers who had no access to the patient's file and were unaware of the cognitive condition of the subjects; each researcher applied one of the following four methods: Manos, 11 Shulman et al, 12 Wolf-Klein et al 13 and Sunderland et al 14 proposals. The fifth researcher applied the Manos method, 11 and thus this test was assessed by two researchers with the aim of evaluating its inter-rater reliability.…”

“…The researchers standardized these different methods by three procedures: 1) reading of the original texts with the description of the items and subsequent studies that used them; 2) intense discussion about the operational aspects to establish standardization in the instrument's application; 3) a pilot project with 35 clock drawings which confirmed that the standardization of these four methods among the members of the research team was excellent. The intraclass correlation coefficient (ICC) results were: 0.96 (95% CI 0.88-0.98); 0.95 (95% CI 0.90-0.98); 0.89 (95% CI 0.79-0.95); 0.97 (95% CI 0.95-0.99) for the Manos, 11 Shulman et al, 12 Wolf-Klein et al, 13 and Sunderland et al…”

“…The Clock Drawing Test (CDT) [10][11][12][13][14] satisfies most of these conditions, and is considered relatively resistant to educational and ethnic diversity, although the available data do not support this observation conclusively. 15,16 Many studies have shown that the CDT is useful as a screening test for cognitive impairment, especially in populations with higher educational levels (8 years or more).…”

“…The objectives of the present study were: 1) to compare the accuracy -sensitivity, specificity, and area under the curve -of four CDT scoring systems (Manos, 11 Shulman,12 Wolf-Klein, 13 Sunderland 14 ); 2) to determine the inter-rater reliability of one of these methods (Manos 11 ); and 3) to determine the influence of schooling on the CDT accuracy as a screening test for dementia in a population of older people treated in a primary care outpatient clinic, where low educational levels predominate.…”

Time that tells: critical clock-drawing errors for dementia screening

“…All CDT systems chosen for comparison have long histories of use, and include one previously shown to be sensitive but less specific (Mendez et al, 1992), one with balanced sensitivity and specificity (Shulman, 2000), and one with high specificity but low sensitivity (Wolf-Klein et al, 1989; data from Scanlan et al, 2002). We then examined the specificity and sensitivity of a revised Mini-Cog (three-item delayed recall + the new CDT algorithm) with the original version.…”