title: Measuring cognitive change with ImPACT: the aggregate baseline approach.
abstract: OBJECTIVE
  The Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) is commonly used to assess baseline and post-injury cognition among athletes in North America. Despite this, several studies have questioned the reliability of ImPACT when given at intervals employed in clinical practice. Poor test-retest reliability reduces test sensitivity to cognitive decline, increasing the likelihood that concussed athletes will be returned to play prematurely. We recently showed that the reliability of ImPACT can be increased when using a new composite structure and the aggregate of two baselines to predict subsequent performance. The purpose of the present study was to confirm our previous findings and determine whether the addition of a third baseline would further increase the test-retest reliability of ImPACT.
  
  
  METHODS
  Data from 97 English speaking professional hockey players who had received at least 4 ImPACT baseline evaluations were extracted from a National Hockey League Concussion Program database. Linear regression was used to determine whether each of the first three testing sessions accounted for unique variance in the fourth testing session.
  
  
  RESULTS
  Results confirmed that the aggregate baseline approach improves the psychometric properties of ImPACT, with most indices demonstrating adequate or better test-retest reliability for clinical use.
  
  
  CONCLUSIONS
  The aggregate baseline approach provides a modest clinical benefit when recent baselines are available - and a more substantial benefit when compared to approaches that obtain baseline measures only once during the course of a multi-year playing career. Pending confirmation in diverse samples, neuropsychologists are encouraged to use the aggregate baseline approach to best quantify cognitive change following sports concussion.
authors.affiliation: a Department of Psychology , University of Missouri - Kansas City , Kansas City , MO , USA.
authors.forename: Jared M
authors.initials: JM
authors.lastname: Bruce
authors.affiliation: a Department of Psychology , University of Missouri - Kansas City , Kansas City , MO , USA.|b Psychological and Neurobehavioral Associates , State College , PA , USA.
authors.forename: Ruben J
authors.initials: RJ
authors.lastname: Echemendia
authors.affiliation: c Faculty of Kinesiology , Sport Injury Prevention Research Centre, University of Calgary , Calgary , Canada.
authors.forename: Willem
authors.initials: W
authors.lastname: Meeuwisse
authors.affiliation: d Faculty of Kinesiology and Physical Education , University of Toronto , Toronto , Canada.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hutchison
authors.affiliation: e Ottawa Sport Medicine Center , Ottawa , Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Aubry
authors.affiliation: d Faculty of Kinesiology and Physical Education , University of Toronto , Toronto , Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Comper
mesh_terms: D001924:Brain Concussion / Q000523:psychology*; D003071:Cognition / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D015203:Reproducibility of Results
keywords: Concussion; ImPACT; baseline; mild traumatic brain injury; reliability