Can You Outsmart the ImPACT Test? A Study of Sandbagging on Baseline Concussion Assessments

Indianapolis, IN

The computerized Immediate Post-concussion Assessment and Cognitive Test (ImPACT), which compares baseline and post-injury performance, is a common method used to aid in concussion diagnosis. The baseline ImPACT assessment has built-in invalidity indicators, designed to flag results which suggest underperformance. Anecdotally, many athletes purposefully sandbag their baseline assessment (perform below their true ability). The manufacturer of ImPACT claims that their built-in validity indicators identify all but ~11% of those attempting to sandbag. Many clinicians feel that number appears to be much higher. Seventy-seven participants completed the randomized, controlled study which involved randomizing participants into a control (do your best) group or the sandbagging group (control n=37, sandbag n=40.) Zero participants in the control group were flagged as having invalid results. Only fifty percent of the purposeful sandbag group was identified by current invalidity indicators. Average composite scores for each assessment category were statistically different between control and sandbagging groups: Memory Verbal Composite (90.03 vs 60.9, P < 0.0001); Memory Visual Composite (81.4 vs 55.27, P < 0.0001); Visual Motor Composite (44.25 vs 28.21, P < 0.0001); Reaction Time Composite (0.556 vs 0.803, P < 0.0001); Impulse Control Composite (5.14 vs 17.85, P < 0.0001). Successful sandbaggers (not flagged as invalid) were more likely to be first time ImPACT takers (P = 0.01) In summary, only half of those attempting to sandbag the baseline ImPACT test are identified by current methods.