Examining the validity of the Delis-Kaplan Executive Function System (D-KEFS) in traumatic brain injury.

This study examines the validity of the Delis-Kaplan Executive Function System (D-KEFS) in a traumatic brain injury (TBI) population compared to participants with orthopaedic injuries and normative controls. The utility of the D-KEFS was examined using a between groups design. One hundred patients with mild uncomplicated to severe TBI were recruited from a consecutive cohort of patients admitted as inpatients to a UK Major Trauma Centre and compared to 823 participants from the D-KEFS normative sample and 26 participants with orthopaedic injuries. Data were filtered for performance validity. Sample discrimination was calculated from D-KEFS subtest scores and derived index scores. Sensitivity to TBI severity was established. The TBI participants performed significantly lower on the D-KEFS Trail Making Test, Colour Word Interference, Colour Word Switching, Letter Fluency and Verbal Fluency Category Switching Total Words Correct. The D-KEFS index scores discriminated between TBI, orthopaedic and normative participants with large and moderate effect sizes, respectively. The D-KEFS demonstrated a dose-response relationship with TBI severity. These effects were robust to differences in premorbid intellectual functioning; however, D-KEFS performance was sensitive to performance on tests of mental processing speed. The use of a D-KEFS index score provides a robust and reliable discrimination of TBI patients from healthy control participants. This discrimination is not accounted for by premorbid intellect or the non-specific effects of trauma. The clinical and conceptual implications of these findings are considered.

Cognitive Outcome After Complicated Mild Traumatic Brain Injury: A Literature Review and Meta-Analysis.

Cognitive outcome for mild traumatic brain injury (mTBI) with positive brain imaging (complicated mTBI) was compared with that for mTBI with normal imaging (uncomplicated mTBI) and with moderate to severe TBI, using meta-analysis. Twenty-three studies utilizing objective neurocognitive tests were included in the analysis. At less than 3 months post-injury, complicated mTBI was associated with poorer cognitive outcomes than uncomplicated mTBI, but deficits were not comparable to those with moderate-severe TBI. After 3 months post-injury, a similar pattern was detected. Beyond 3 months, deficits in complicated mTBI relative to those with uncomplicated mTBI were present in processing speed, memory, executive function, and language, although the latter may be the result of reduced semantic fluency. The effect size of deficits in these domains was more marked in moderate-severe TBI. The available data support the use of complicated mTBI as a distinct classification in the prediction of cognitive outcome. The extent of cognitive deficit in complicated mTBI was small and unlikely to cause significant disability. However, patients with complicated mTBI constitute a broad category encompassing individuals who may differ markedly in the nature and extent of intracranial imaging abnormality, and further studies are warranted. Limitations of the available studies include small, selected samples; variations in TBI severity classification; absence of validity ("effort") testing; differing imaging methodology; and lack of long-term follow-up.

Validation of the Neuropsychological Assessment Battery Screening Module (NAB-SM) in patients with traumatic brain injury.

This study cross-validates the screening module of the Neuropsychological Assessment Battery (NAB-SM) with a battery of well validated neuropsychological tests (Convergent Validity Test Battery: CVTB) in a Traumatic Brain Injury (TBI) population. Forty-four participants with "mild-complicated" to "severe" TBI were recruited from a cohort of patients attending an outpatient clinic at a UK major trauma center. The NAB-SM Total Index score and an abbreviated short-form, from which a TBI Index was derived, both showed good classification accuracy in predicting impairment as measured by the CVTB mean score. These indices also accurately identified impairment as defined by the base rate of low scores across individual CVTB indices measuring mental processing speed, working memory, memory and executive functioning. The NAB-SM and its derived TBI index therefore have significant utility as a cognitive screening tool for use in either inpatient (acute) or outpatient TBI populations.