Deficits in Processing Speed and Decision Making in Relapsing-Remitting Multiple Sclerosis: The Digit Clock Drawing Test (dCDT)

The current research assessed how digital clock drawing test (dCDT) parameters compliment and convey additional information in conjunction with traditional clock drawing scoring methods in patients with multiple sclerosis (MS). MS and normal control (NC) clock drawing performance was initially scored using a 10-point scale where NC test performance classified MS patients into impaired versus non-impaired clock drawing groups. dCDT variables included intra-component latencies or the time elapsed between clock drawing components (i.e., time between last element drawn followed by the first clock hand); inter-digit latency (i.e., average time between drawing numbers; and quartile drawing time (i.e., total drawing time divided into four equal segments. Subsequent analyses assessed dCDT parameters and other neuropsychological tests related to deficits in processing speed and other neurocognitive functions. In the command condition impaired MS patients produced slower selected intracomponents and slower 3rd and 4th quartile latencies (p<0.032) compared to other groups. In the copy condition impaired MS patients also displayed slower selected intra-components and slower latencies in all four quartiles compared to NCs (p<0.003), but slower latencies only for the 3rd and 4th quartiles compared to non-impaired MS patients (p<0.016). Regression analyses associated slower combined intra-component latencies with reduced processing speed (Symbol Copy, WAIS-R-NI), category (‘animal’) fluency, and CVLT recognition discriminability, and the propensity to endorse selected CVLT list B recognition foils. The dCDT compliments traditional clock scoring methods, captures behavior previously unobtainable, and is related to processing speed and dysexecutive impairment known to be present in MS.