Interpreting clinical reaction time change and recovery after concussion: A baseline versus norm- based cutoff score comparison

Context: Preseason testing can be time intensive and cost prohibitive. Therefore, using normative data for postconcussion interpretation in lieu of preseason testing is desirable. Objective: To establish the recovery trajectory for clinical reaction time (RTclin) 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. Design: Case-control study. Setting: Multisite clinical setting. Patients or Other Participants: An 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 RTclin (ie, postconcussion or year 2) was compared with the individual year 1 preseason baseline RTclin and normative baseline data (ie, sex and sport specific). Receiver operating characteristic curves were calculated to compare the sensitivity and specificity of RTclin change from baseline and norm-based cutoff scores. Results: Clinical 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). Conclusions: Norm-based cutoff scores can be used for interpreting RTclin scores postconcussion in collegiate athletes when individual baseline data are not available, although low sensitivity and specificity limit the use of RTclin as a stand-alone test.