Screening for early cognitive impairment in multiple sclerosis patients using the clock drawing test

The clock drawing test (CDT) is a complex task assessing integrative functions, abstract thinking and visuospatial organization. In the present study we evaluated the CDT as a possible screening instrument for early cognitive impairment in multiple sclerosis (MS) patients. In total, 107 MS patients completed the CDT as well as a battery assessing five cognitive domains. There were 73 female and 34 male participants (mean age 45.4+/-11.6 years, range 19-69). The majority (76/107) were diagnosed with a relapsing-remitting disease course. Mean expanded disability status scale (EDSS) score was 4.3+/-2.4 (range 0-8). The CDT was scored on a 1-6 point scale with "1" being a perfect score and "6" reflecting severe disorganization. Mean CDT score was 2.6+/-1.4. In 53% of patients the CDT was normal while in 11.2% dementia was apparent. The CDT score did not correlate with the total EDSS. Significant correlations were obtained with the mental functional system score of the EDSS (r = 0.78; p = 0.0001), visual learning and recall, sustained attention and concentration. Our findings demonstrate the sensitivity of the CDT to several cognitive domains. The absence of correlation with total EDSS score coupled with significant correlation with the mental functional system suggests that the CDT may be useful for screening MS patients.