Background Concussion head injuries are common in high school athletes. The Sport Concussion Assessment Tool – 2 (SCAT2) has been recommended and widely adopted as a standardised method of evaluating an injured athlete with a suspected concussion. Sideline return to play decisions can hinge on the results of a SCAT2 score. However, most athletes will not have had baseline testing performed for comparison if injury occurs. Therefore, establishing of age-, sex- and sport-matched normative data for the high school athlete population is critical.

Purpose To determine baseline scores in all SCAT2 domains among high school athletes with no prior history of a concussion and to examine subgroup differences for girls and boys, age and sport to establish normative ranges.

Materials and methods The SCAT2 was administered to 214 high school athletes (155 males and 59 females) who participated in football, women's soccer, men's basketball, gymnastics, baseball, softball and track with no prior history of concussion. There were 111 athletes in the 13–15-year-old cohort and 103 in the 16–19-year-old group with a mean age of 15.7 years of age. In all SCAT2 domains the mean and SD of the results were determined. The domains were analysed using age, sex and sport as covariates. Component parts of the cognitive (concentration) domain (digit sequencing and months of year in reverse order) were also analysed by age, sex and sport. The percentage of high school athletes able to perform each digit-sequencing test was calculated as was the percentage of participants who could recite the months of the year in reverse order.

Results The average SCAT2 score for these high school athletes was 89 of a possible 100 with a SD of 6 units. Athletes reported two or three symptoms at baseline with older students reporting more symptoms than younger ones. The average balance score was 25.82 (of 30), and all athletes were able to complete the double-leg stance. Females scored significantly higher on the balance, immediate memory and concentration scores. Concentration scores in non-concussed high school athletes were low. Only 67% of high school athletes could recite the months of the year backward and only 41% could correctly sequence 5 digits backward. Only 55% of high school football players could correctly recite the months of the year backward and 32% could sequence 5 digits.

Conclusions Non-concussed high school athletes scored near the total possible in most domains of the SCAT2 with the exception of concentration testing and balance testing. All athletes were able to complete the double-leg stance at baseline; however, there was significant variability of tandem and single-leg stance. Baseline testing is important when considering balance tests. Concentration testing in high school athletes is unreliable because of high baseline error and is likely to result in a high rate of false positives and false negatives. Return to play decisions should not rely on concentration testing without a baseline test for comparison.