A modified Stroop test may be a worthwhile addition to off-field concussion screening, according to a study conducted over two seasons of the Super Rugby competition in five countries including Australia.
The study, published in the Journal of Science and Medicine in Sport, said current off-field concussion screening tools have sub-optimal accuracy.
The investigators, including Associate Professor Andrew Gardner from Hunter New England Sports Concussion Clinic and Dr Warren McDonald, chief medical officer from Rugby Australia, compared previously unvalidated, abridged versions of the Trail Making, Stroop, and Corsi block tapping cognitive tests. The tests were modified to take 1-2 mins each.
The tests were conducted in pre-season baseline testing in 643 rostered players and in 10–15 minute off-field assessments in 127 players with a head impact event with the potential for concussion but without clear signs of concussion requiring immediate removal from play.
Concussion was later confirmed in 33 players following post-match and 48 hour assessments by the team doctors
The study found only the modified 10-word Stroop test – a colour-word interference task which measures selective attention, mental flexibility, and inhibitory control – could distinguish between concussed and non-concussed players ((median time to complete 21.1 v 18.4 sec, p < 0.01, AUROC 0.66).
The study found the existing World Rugby Head Injury Assessment (HIA-1) had a sensitivity of 78.8% (95% CI 61.1–91.0%) and specificity of 64.2% (51.5–75.5%, n = 100) for the detection of concussion in included players.
“Adding time to complete the Stroop Test to the HIA-1 screening tool using its normative threshold resulted in the detection of 2 additional concussion cases, at the cost of 4 false positives (combined sensitivity of 84.8%, specificity 58.2%, AUROC 0.72).”
The investigators said processing of the Stroop task was performed by the anterior cingulate cortex and the dorsolateral prefrontal cortex.
“Impairment in both of these cerebral regions has been observed in human MRI imaging studies, and animal models, following mild traumatic brain injury. Although evidence is limited in concussion and mild head injury, studies have shown worsened performance in the traditional Stroop task in moderate and severe traumatic brain injuries.”
Neither the abridged Spatial Memory and TMT-B tests distinguished between uninjured and injured players.
Co-investigator and clinical neuropsychologist Associate Professor Gardner told the limbic that the findings could be widely implemented across a variety of sports.
“The injury is treated very similarly across all of the contact and collision sports. Certainly with AFL, NRL and rugby but also soccer and cricket…something that gets implemented in one sport, gets reviewed by other sports as well.”