The Development and Psychometric Evaluation of a Supplementary Index Score of the Neuropsychological Assessment Battery Screening Module that is Sensitive to Traumatic Brain Injury

Objective: This study examines the validity of the NAB Screening Module (screening module of the neuropsychological assessment battery, S-NAB) in an acute traumatic brain injury (TBI) inpatient population and provides psychometric evaluation of an original index sensitive to TBI impairment.

Method: The utility of the S-NAB as a TBI screen was examined using a between groups design. One-hundred and four patients with mild complicated to severe TBI were recruited from a consecutive cohort of patients admitted as inpatients to a UK Major Trauma Centre. Ninety-eight control participants were selected from the S-NAB normative sample. All TBI patients completed the S-NAB during their inpatient stay.

Results: Control participants scored significantly higher than TBI participants on the Total Screening index (t = 3.626, p < 0.01), The Attention index (t = 7.882, p < 0.01), and the Executive index (t = 5.577, p < 0.01). A briefer TBI Impairment index of six subtests was constructed which accurately discriminated TBI patients from normative controls (t = 9.9, p < 0.01; Cohen's d = 1.54). The TBI index had excellent classification accuracy (AUC = 0.83), superior to that of the standard S-NAB indices. The TBI Index, Attention Index, and Total Screening Index demonstrated increasing impairment with increased severity of injury.

Conclusions: The S-NAB TBI index is a robust, reliable screening index for use with acute TBI patients, which is sensitive to the effects of acute TBI. It affords a briefer cognitive screen than the S-NAB and demonstrates a dose response relationship to TBI severity.