Abstract:
BACKGROUND: Test-retest reliability is a critical issue in the utility of computer-based neurocognitive assessment paradigms employing baseline and postconcussion tests. Researchers have reported low test-retest reliability for the Immediate Post Concussion Assessment and Cognitive Testing (ImPACT) across an interval of 45 and 50 days. PURPOSE: To re-examine the test-retest reliability of the ImPACT between baseline, 45 days, and 50 days. STUDY DESIGN: Descriptive laboratory study. METHODS: Eighty-five physically active college students (51 male, 34 female) volunteered for this study. Participants completed the ImPACT as well as a 15-item memory test at baseline, 45 days, and 50 days. Intraclass correlation coefficients (ICCs) were calculated for ImPACT composite scores, and change scores were calculated using reliable change indices (RCIs) and regression-based methods (RBMs) at 80% and 95% confidence intervals (CIs). RESULTS: The respective ICCs for baseline to day 45, day 45 to day 50, baseline to day 50, and overall were as follows: verbal memory (0.76, 0.69, 0.65, and 0.78), visual memory (0.72, 0.66, 0.60, and 0.74), visual motor (processing) speed (0.87, 0.88, 0.85, and 0.91), and reaction time (0.67, 0.81, 0.71, and 0.80). All ICCs exceeded the threshold value of 0.60 for acceptable test-retest reliability. All cases fell well within the 80% CI for both the RCI and RBM, while 1% to 5% of cases fell outside the 95% CI for the RCI and 1% for the RBM. CONCLUSION: Results suggest that the ImPACT is a reliable neurocognitive test battery at 45 and 50 days after the baseline assessment. The current findings agree with those of other reliability studies that have reported acceptable ICCs across 30-day to 1-year testing intervals, and they support the utility of the ImPACT for the multidisciplinary approach to concussion management. CLINICAL RELEVANCE: This study suggests that the computerized neurocognitive test battery, ImPACT, is a reliable test for postconcussion serial assessments. However, when managing concussed athletes, the ImPACT should not be used as a stand-alone measure.