Objective Analysis of a proposed method for classifying invalid baseline tests in professional football players.

Design Retrospective cross-sectional study.

Setting Professional Canadian Football.

Participants Four hundred and seventy-eight male football players from the Canadian Football League.

Intervention A proposed system to classify invalid baselines used the lowest 5% of domain scores from baseline Immediate Post-concussion Assessment and Cognitive Testing (ImPACT), King Devick, and SCAT3 (balance and SAC totals) coupled with the highest 5% of total symptom report from SCAT3. Impairment on 2 or more scores was classified as invalid (INV).

Main Outcome measures Descriptive statistics, correlation and stepwise regression analysis.

Main Results Correlations revealed significant relationships (p<0.05) between INV and all 5 domains of ImPACT and SCAT3 symptom score, but not for King Devick and SCAT3 balance and SAC totals. The forward stepwise regression yielded a significant model (R2=0.23, F(4, 473)=35.7, p<0.001). Significant predictors included visual memory, reaction time, impulse control, and verbal memory from ImPACT. This system classified 3.7% of participant with invalid baseline tests.

Conclusions There are few published methodologies used to classify invalid baseline tests in spite of their widespread use. Valid baseline tests are essential for proper identification and management of concussion. Our proposed method identified 4 ImPACT domains scores that predict invalid baseline scores. This system may be helpful in classifying invalid baseline tests with commonly used baseline test measures although more research is required to validate this method.

Competing interests None.