Sandbagging ImPACT

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Half of Purposeful Sandbaggers Undetected by ImPACT’s Embedded Invalidity Indicators

Amy Peak Director of undergraduate health science programs Butler University

Courtney Raab  Indiana University medical student


Objective: The primary objective of this study is to determine the ability of embedded invalidity indicators (EIIs) within the Immediate Post-concussion Assessment and Cognitive Test (ImPACT) to accurately identify individuals purposefully underperforming (sandbagging) on the baseline assessment.  The secondary objective is to determine if any of the five specific EIIs are more or less likely to identify purposeful sandbaggers.

Background: Sandbagging baseline neuropsychological tests is a growing problem with significant potential consequences including premature post-concussion clearance.

Design/Methods:  Volunteers were recruited to complete a baseline ImPACT assessment.  Participants were randomized to either a control group or a coached sandbagging group.  Primary outcome measures were the number of participants identified as invalid via any EII, as well as mean raw composite scores and percentiles for each sub-section within the ImPACT assessment.

Results: Seventy-seven participants (37 control and 40 sandbaggers) completed the study. Only half (50%, n=20) of the purposeful sandbaggers were identified via any EII. Appropriately, no participants in the control group were identified as invalid. The Working Memory EII correctly identified 40% of the purposeful sandbaggers, and the Three Letters EII identified 35% of purposeful sandbaggers. All other EIIs identified < 15% of purposeful sandbaggers. Twenty-six purposeful sandbaggers achieved at least one composite sub-score <1st percentile; 27% of those were not identified via any EII. One participant scored < 1st percentile in every composite category and was not identified via any EII.

Conclusion:  Sandbagging baseline ImPACT assessments without detection likely occurs more often than previous literature suggests.  Half of purposeful sandbaggers were not identified via current EIIs, and three of five EIIs identified < 15% of purposeful sandbaggers. Re-evaluation or recalibration of ImPACT’s current EIIs may be appropriate.


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