title: Long-term Stability and Reliability of Baseline Cognitive Assessments in High School Athletes Using ImPACT at 1-, 2-, and 3-year Test-Retest Intervals.
abstract: OBJECTIVE
  The ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing) neurocognitive testing battery is a widely used tool used for the assessment and management of sports-related concussion. Research on the stability of ImPACT in high school athletes at a 1- and 2-year intervals have been inconsistent, requiring further investigation. We documented 1-, 2-, and 3-year test-retest reliability of repeated ImPACT baseline assessments in a sample of high school athletes, using multiple statistical methods for examining stability.
  
  
  METHODS
  A total of 1,510 high school athletes completed baseline cognitive testing using online ImPACT test battery at three time periods of approximately 1- (N = 250), 2- (N = 1146), and 3-year (N = 114) intervals. No participant sustained a concussion between assessments.
  
  
  RESULTS
  Intraclass correlation coefficients (ICCs) ranged in composite scores from 0.36 to 0.90 and showed little change as intervals between assessments increased. Reliable change indices and regression-based measures (RBMs) examining the test-retest stability demonstrated a lack of significant change in composite scores across the various time intervals, with very few cases (0%-6%) falling outside of 95% confidence intervals.
  
  
  CONCLUSIONS
  The results suggest ImPACT composites scores remain considerably stability across 1-, 2-, and 3-year test-retest intervals in high school athletes, when considering both ICCs and RBM. Annually ascertaining baseline scores continues to be optimal for ensuring accurate and individualized management of injury for concussed athletes. For instances in which more recent baselines are not available (1-2 years), clinicians should seek to utilize more conservative range estimates in determining the presence of clinically meaningful change in cognitive performance.
authors.affiliation: Semmes Murphey Neurologic and Spine Institute, Memphis TN, USA.|Department of Counseling, Educational Psychology and Research, The University of Memphis, Memphis TN, USA.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Brett
authors.affiliation: Department of Psychology, Saint Joseph's University, Philadelphia, PA, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Smyk
authors.affiliation: Department of Neurological Surgery, Vanderbilt University School of Medicine, Nashville, TN, USA.|Vanderbilt Sports Concussion Center, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Solomon
authors.affiliation: Semmes Murphey Neurologic and Spine Institute, Memphis TN, USA.|Department of Neurosurgery, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Brandon C
authors.initials: BC
authors.lastname: Baughman
authors.affiliation: Department of Psychology, Saint Joseph's University, Philadelphia, PA, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Schatz
keywords: Assessment; Childhood brain insult; Head injury; Norms/normative studies; Practice effects/reliable change; Test construction; Traumatic brain injury