Investigating the validity of the Delis-Kaplan Executive Function System (D-KEFS) as a neuropsychological assessment tool for executive functions in the traumatic brain inhury (TBI) in the UK

Chan, Yin Ming (2019). Investigating the validity of the Delis-Kaplan Executive Function System (D-KEFS) as a neuropsychological assessment tool for executive functions in the traumatic brain inhury (TBI) in the UK. University of Birmingham. Clin.Psy.D.

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Abstract

Background:
Deficits in executive functioning is highly prevalent in people with Traumatic Brain Injury (TBI). The Delis Kaplan Executive Function (D-KEFS) comprises a standardised set of tests designed to measure a wide spectrum of abilities associated with executive functioning. Currently there is substantial evidence to support the validity of D-KEFS as a useful instrument to identify deficits in executive functioning. This study aims to investigate the validity of the D-KEFS by comparing the performance of a sample of patients with mild-uncomplicated to severe TBI, with that of orthopaedic controls using selected D-KEFS subtests. The orthopaedic patients are considered as ‘gold standard’ controls for studying TBI given they are arguably representative of the TBI group both demographically and psychosocially.

Methods:
One hundred patients with mild-uncomplicated to severe Traumatic Brain Injury (TBI) and twenty-six orthopaedic patients were recruited. Measures of performance validity were administered to participants. Those who failed the tests were excluded from the study. Selected D-KEFS subtests (Trail Making, Verbal Fluency, Colour Word Interference Test and Tower Test) were administered to both TBI and orthopaedic controls, as well as the application of additional measures of premorbid intellectual functioning and mental processing speed to account for other influences on D-KEFS performance that were not specific to executive functioning.

Results:
The TBI participants performed significantly worse than the orthopaedic controls on the Trail Making Number-Letter Switching, Colour Word Interference Inhibition, Colour Word Interference Inhibition/ Switching, Letter Fluency and Category Switching tasks, but not on Category Fluency and Tower Test. The Executive Functioning Indices (EFIs) constructed also demonstrated significant group mean differences, with TBI patients performing worse than the orthopaedic controls. More importantly the composite EFIs resulted in greater effect sizes than the individual subtests. Notably, group differences vanished when the effect of processing speed was controlled for. Lastly, the results also indicated that the TBI group presented with a consistently higher rate of obtaining low scores in comparison to the orthopaedic controls.

Conclusions:
To our knowledge this is the first study in the UK that has compared the performance of a sample of patients with mild-uncomplicated to severe TBI, with that of orthopaedic controls using D-KEFS. Relative to the orthopaedic controls the TBI patients showed marked deficits in executive functioning across some subtests as well as in EFIs, with moderate to large effect sizes. These findings support the use of the D-KEFS EFIs for the assessment of executive functioning in TBI population. Future study might consider using a larger and more gender balanced orthopaedic population and also examine the performances of TBI individuals suffering head trauma of various aetiologies on D-KEFS in order to capture a more comprehensive cognitive profile for this population group.

Type of Work:

Thesis (Doctorates > Clin.Psy.D.)

Award Type:

Doctorates > Clin.Psy.D.

Supervisor(s):