Screening for Early Alzheimer's Disease in Elderly Chinese Patients Using the Chinese Clock Drawing Test

Article excerpt

Abstract

Objective: Alzheimer's disease is an increasing problem among the Chinese population. Earlier intervention will reduce the burden of the disease for patients, their families, and society. In this study, the usefulness of the Clock Drawing Test for screening for early Alzheimer's disease was examined.

Patients and Methods: The Clock Drawing Test and Clock Copying Test were administered to 66 elderly Chinese patients with early Alzheimer's disease and 66 age-matched, community-dwelling, elderly Chinese people without dementia for comparison. The Chinese Clock Drawing Test scoring criteria were used.

Results: Significant differences in Clock Drawing Test scores were found between patients with Alzheimer's disease and controls (p < 0.001). Clock Drawing Test performances were significantly correlated with educational level in both groups. Optimal cut-off points for participants for different educational levels were identified. The sensitivities of the Clock Drawing Test for screening for early Alzheimer's disease among participants with minimal (<2 years) and elementary (2 to 6 years) education were 72.8% and 75.0%, respectively. Positive predictive values obtained by combining the Clock Drawing Test and Clock Copying Test were 73.9% and 95.2% for participants with minimal and elementary education, respectively.

Conclusions: The Clock Drawing Test is a useful tool for screening for early Alzheimer's disease among the elderly Chinese population with elementary educational level. The potential usefulness for differentiating dementia subtypes, particularly in combination with other screening tools, should be further explored.

Key words: Alzheimer disease, Diagnosis

Introduction

Traditionally, the Clock Drawing Test (CDT) has been used to reflect parietal lobe function and to examine for visuo-spatial inattention. (1,2) Although clock drawing is most often thought of as constructional in nature, the ability to draw an intact clock face is a complex task requiring the integrity of different cognitive domains. (3) The CDT is a potential measure of global cognitive function for epidemiological studies because it is easy and quick to administer, and is relatively unaffected by language, cultural, or ethnic factors. The test can be reliably rated both by clinicians and trained observers, and generally has good inter-rater and test-retest reliability. The CDT also provides objective and graphic documentation of cognitive deficits that can be shared by the clinician with patients and family members. (4-8)

Studies have been performed to investigate the effectiveness of the CDT for recognising the early stage of dementia. Although the CDT is well known as a screening test for cognitive impairment and dementia, assessment of its validity for early diagnosis of the disorder is limited. (5,9-13) In this study, we explored the potential use of the CDT and Clock Copying Test (CCT) for screening for early Alzheimer's disease (AD) in the elderly Chinese population, among which a relatively low literacy level is expected. To explore the effect of educational level on the performance of the CDT and CCT, patients were divided into 3 groups according to their educational level, and the applicability of the CDT for each group was studied.

Patients and Methods

Patients

Two groups of elderly Chinese people who had participated in a project to examine the behavioural and psychological symptoms of AD were recruited from October 2000 to June 2002. The first group comprised 66 patients with early AD (Clinical Dementia Rating [CDR], 1 (14)) who first presented to the psychogeriatric clinics at hospitals in the New Territories East region of Hong Kong. Sixty six cognitively intact, age-matched elderly people (CDR, 0) were recruited from local elderly social centres for comparison. Patients with profound sensory deficits or history of significant head injury or neurological disorder were excluded. …