Clinical Reaction Time After Concussion: Change From Baseline Versus Normative-Based Cutoff Scores.

CONTEXT: Pre-season testing is often used to establish baseline scores for post-concussion interpretation. However, pre-season testing can be time-intensive and cost-prohibitive, in which case normative data may be used for post-injury interpretation.

OBJECTIVE: To compare change from baseline and normative-based cutoff scores in interpreting clinical reaction time (RTclin) following concussion.

DESIGN: Prospective case-control study.

SETTING: Multi-site study with testing completed in university athletic training rooms.

PATIENTS OR OTHER PARTICIPANTS: An overlapping sample of 99 participants (age=19.0±1.1 years) evaluated within 6 hours post injury, 176 participants (age 18.9±1.1 years) evaluated 24-48 hours post injury, and 214 participants (18.9±1.1 years) evaluated at the time they were cleared to begin a return-to-play progression. Concussion participants were compared to 942 control participants (age=19.0±1.0 years) who did not sustain a concussion during the study period but completed preseason baseline testing one year apart.

MAIN OUTCOME MEASURES: At each time point, follow-up RTclin (i.e., post injury or year 2) was compared to individualized year 1 preseason baseline RTclin and to normative baseline data (i.e., sex- and sport-specific). Receiver operating characteristic curves were used to compare sensitivity and specificity of RTclin change from baseline and normative-based cutoff scores.

RESULTS: Within 6h, change from baseline of 16ms maximized combined sensitivity (52%) and specificity (78%, AUC=0.702), while normative-based cutoff scores of 19ms maximized combined sensitivity (45%) and specificity (86%, AUC=0.700). At 24-48h, change from baseline of 2ms maximized combined sensitivity (64%) and specificity (61%, AUC=0.666), while normative-based cutoff scores of 0ms maximized combined sensitivity (63%) and specificity (62%, AUC=0.647).

CONCLUSIONS: Normative-based cutoff scores can be used for interpreting RTclin scores following concussion when individualized baseline data is not available, although low sensitivity and specificity may limit clinical use as a stand-alone test.