Interpreting Clinical Reaction Time Change and Recovery After Concussion: A Baseline Versus Norm-Based Cutoff Score Comparison

ContextPreseason testing can be time intensive and cost prohibitive. Therefore, using normative data for postconcussion interpretation in lieu of preseason testing is desirable.ObjectiveTo establish the recovery trajectory for clinical reaction time (RT_clin) and assess the usefulness of changes from baseline (comparison of postconcussion scores with individual baseline scores) and norm-based cutoff scores (comparison of postconcussion scores with a normative mean) for identifying impairments postconcussion.DesignCase-control study.SettingMultisite clinical setting.Patients or Other ParticipantsAn overlapping sample of 99 participants (age = 19.0 ± 1.1 years) evaluated within 6 hours postconcussion, 176 participants (age = 18.9 ± 1.1 years) evaluated at 24 to 48 hours postconcussion, and 214 participants (age = 18.9 ± 1.1 years) evaluated once they were cleared to begin a return-to-play progression were included. Participants with concussion were compared with 942 control participants (age = 19.0 ± 1.0 years) who did not sustain a concussion during the study period but completed preseason baseline testing at 2 points separated by 1 year (years 1 and 2).Main Outcome Measure(s)At each time point, follow-up RT_clin (ie, postconcussion or year 2) was compared with the individual year 1 preseason baseline RT_clin and normative baseline data (ie, sex and sport specific). Receiver operating characteristic curves were calculated to compare the sensitivity and specificity of RT_clin change from baseline and norm-based cutoff scores.ResultsClinical reaction time performance declined within 6 hours (18 milliseconds, 9.2% slower than baseline). The decline persisted at 24 to 48 hours (15 milliseconds, 7.6% slower than baseline), but performance recovered by the time of return-to-play initiation. Within 6 hours, a change from baseline of 16 milliseconds maximized combined sensitivity (52%) and specificity (79%, area under the curve [AUC] = 0.702), whereas a norm-based cutoff score of 19 milliseconds maximized combined sensitivity (46%) and specificity (86%, AUC = 0.700). At 24 to 48 hours, a change from baseline of 2 milliseconds maximized combined sensitivity (64%) and specificity (61%, AUC = 0.666), whereas a norm-based cutoff score of 0 milliseconds maximized combined sensitivity (63%) and specificity (62%, AUC = 0.647).ConclusionsNorm-based cutoff scores can be used for interpreting RT_clin scores postconcussion in collegiate athletes when individual baseline data are not available, although low sensitivity and specificity limit the use of RT_clin as a stand-alone test.