Reliability and Validity of the Sport Concussion Assessment Tool-3 (SCAT3) in High School and Collegiate Athletes
Chin EY., Nelson LD., Barr WB., McCrory P., McCrea MA. Am J Sport Med. 2016; ahead of print
Take Home Message: A clinician needs to recognize that sex, competitive level, and attention deficit/hyperactivity disorder or learning disorder may influence SCAT3 scores. A medical professional could use normative conversion tables if they lack baseline scores and may not need to worry about practice effects with the SCAT3, except when retesting an athlete within 7 days.
The SCAT3 is a free and easy to administer test for sideline clinical assessment of concussed athletes. However, there is little published on what factors influence SCAT3 scores or how to interpret the SCAT3 and each subcomponents (sign and symptom score, SAC, modified BESS). Therefore, the authors collected 2,018 baseline SCAT3 exam scores from 9 high schools and 4 colleges (from August 2012 to October 2014) to evaluate predictors of baseline performance, reliability, and strategies to interpret scores (e.g., identifying reliable chance index cutoffs). From this sample (77% male), 166 athletes, who suffered a concussion during the study period (84% male), were re-evaluated within 24 hours of injury and at days 8, 15, and 45 after injury. These athletes were matched to noninjured peers (164 athletes; 83% male). Noninjured athletes were re-evaluated as soon as identified as a control and then at 7, 14, and 44 days later. The authors found that the sign and symptoms score component best discriminated between concussed and nonconcussed athletes compared with SAC and BESS. Athletes that scored higher on baseline symptom severity were females, high school athletes, and athletes with attention-deficit/hyperactivity disorder or learning disorder compared with males, collegiate athletes, and those without attention-deficit/hyperactivity disorder or learning disorder, respectively. Athletes that scored low on the baseline SAC component were male, had attention-deficit/hyperactivity disorder, or had a learning disorder. Athletes that performed worse on the baseline BESS component were male, high school athletes, or diagnosed with attention deficit/hyperactivity disorder or learning disorder. Modified and full BESS test scores were the most reliable components of the SCAT3. The authors also observed practice effects for the SAC and full BESS for day 7, but they found no evidence of a practice effect when the tests were administered with a longer time in between testing. Normative data by sex and level of competition were derived from athletes without attention-deficit/hyperactivity disorder or learning disorder. A common guideline for interpreting performance level by percentile was calculated, where a score of 2-8% was deemed borderline, and less than 2% was impaired based on normative data.
Overall, the authors demonstrated in a large cohort that sex, level of competition, and history of attention-deficit/hyperactivity disorder or learning disorder are predictors of SCAT3 performance. The authors also suggest that baseline testing is not better than comparing post injury performance to normative data. This allows flexibility in how medical professionals handle concussion assessment and reevaluations. Medical professionals could interpret SCAT3 scores using reliable change index if they have baseline data, or use normative tables if they do not have baseline data. It will be ideal if the normative data tables were publicly available for free. Additionally, they determined that the sign and symptom score is the most sensitive for detecting a concussion; therefore, it is important that athletes understand all the possible concussion sign and symptoms that could follow a head impact since the self-report symptom is still a key component of the concussion assessment. Lastly, the SCAT3 seems to be a reliable tool, as long as you wait a week in-between evaluations to avoid a practice effect. In summary medical professionals should be aware of the factors that may influence SCAT3 scores and determine which way to use the SCAT3 in his/her concussion protocol (e.g., with normative data or baseline scores). Finally, clinicians need to educate athletes on the signs and symptoms of a concussion injury.
Questions for Discussion: Would you still use baseline data if normative tables were available? Do you perform the full BESS or modified BESS when using the SCAT3?
Written by: Jane McDevitt, PhD
Reviewed by: Jeff Driban